Oct. 1994, 日本真空協会, 第19回熊谷記念真空科学論文賞　　　　　　　　　　　　　　　
GaAs(110)微傾斜面上のAlGaAs分子線成長と量子細線構造の形成
中島 尚男;木村 憲泰;佐藤 正道;岩根 正晃;井上 恒一;前橋 兼三;長谷川 繁彦;松田 理;邑瀬 和生

Semiconductor physics: Plasma, thermal, elastic, and acoustic phenomena
J. Zakrzewski, M. Pawlak, O. Matsuda, D. Todorovic, J. Liu
Journal of Applied Physics, 28 Sep. 2024
Scientific journal

Time-resolved imaging of GHz acoustic vibrations at arbitrary frequencies using asynchronous periodic probe laser pulses
Osamu Matsuda, Shohei Ueno, Motonobu Tomoda, Paul H. Otsuka, Oliver B. Wright
Applied Physics Letters, 29 Jul. 2024
Scientific journal

Phononic band calculations and experimental imaging of topological boundary modes in a hexagonal flexural wave machine
Hayato Takeda, Ryoya Minami, Osamu Matsuda, Oliver B. Wright, Motonobu Tomoda
Applied Physics Express, 01 Jan. 2024
Scientific journal

Tomographic reconstruction of picosecond acoustic strain pulses using automated angle-scan probing with visible light
Motonobu Tomoda, Hiroyuki Matsuo, Osamu Matsuda, Roberto Li Voti, Oliver B. Wright
Photoacoustics, Dec. 2023
English, Scientific journal

Spectral analysis of amplitude and phase echoes in picosecond ultrasonics for strain pulse shape determination
Takehiro Tachizaki, Jeremy J. Baumberg, Osamu Matsuda, Motonobu Tomoda, Hirotsugu Ogi, Oliver B. Wright
Photoacoustics, 34, 100566, 100566, Elsevier BV, Dec. 2023
Scientific journal

Optical polarization perturbed by shear strains of ultrasonic bulk waves in anisotropic semiconductors: Multiphysics modeling and optoacoustic validation
Yi He, Hoon Sohn, Osamu Matsuda, Zhongqing Su
Photoacoustics, Aug. 2023
English, Scientific journal

Imaging phonon eigenstates and elucidating the energy storage characteristics of a honeycomb-lattice phononic crystal cavity
P.H. Otsuka, R. Chinbe, M. Tomoda, O. Matsuda, Y. Tanaka, D.M. Profunser, S. Kim, H. Jeon, I.A. Veres, A.A. Maznev, O.B. Wright
Photoacoustics, Jun. 2023
English, Scientific journal

Time-domain Brillouin imaging of sound velocity and refractive index using automated angle scanning
Motonobu Tomoda, Akihisa Kubota, Osamu Matsuda, Yoshihiro Sugawara, Oliver B. Wright
Photoacoustics, Jun. 2023
English, Scientific journal

Sound velocity mapping from GHz Brillouin oscillations in transparent materials by optical incidence from the side of the sample
Motonobu Tomoda, Akira Toda, Osamu Matsuda, Vitalyi E. Gusev, Oliver B. Wright
Photoacoustics, 30, 100459, 100459, Elsevier {BV}, Apr. 2023
English, Scientific journal

Refraction, beam splitting and dispersion of GHz surface acoustic waves by a phononic crystal
Osamu Matsuda, Hiroaki Koga, Hiroki Nishita, Motonobu Tomoda, Paul H. Otsuka, Oliver B. Wright
Photoacoustics, Apr. 2023
Scientific journal

Tapered rainbow metabeam for wideband multimode acoustic blocking based on quadruple-mode resonators
Hayato Takeda, Eikai Murakami, Motonobu Tomoda, Osamu Matsuda, Kentaro Fujita, Oliver B. Wright
Applied Physics Letters, 26 Sep. 2022
Scientific journal

Compact acoustic metamaterial based on the 3D Mie resonance of a maze ball with an octahedral structure
Ting Zhang, Eun Bok, Motonobu Tomoda, Osamu Matsuda, Jianzhong Guo, Xiaojun Liu, Oliver B Wright
Applied Physics Letters, 120, 16, 161701, 161701, {AIP} Publishing, 18 Apr. 2022
Scientific journal

Specular Acoustic Vibrational Wave Transmissions with the Presence of Phononic Bandgaps
Hai Jun Cho, Yuzhang Wu, Jiajun Qi, Yuna Kim, Hiromichi Ohta, Osamu Matsuda
Journal of the Physical Society of Japan, 91, 1, Physical Society of Japan, 15 Jan. 2022
Scientific journal

Gigahertz Optomechanical Photon–Phonon Transduction between Nanostructure Lines
Yuta Imade, Vitalyi E. Gusev, Osamu Matsuda, Motonobu Tomoda, Paul H. Otsuka, Oliver B. Wright
Nano Letters, 21, 14, 6261, 6267, American Chemical Society ({ACS}), 28 Jul. 2021
English, Scientific journal

Coherent phonon detection gated by transient spin-polarized electrons
C. Li, R. T. Harley, P. G. Lagoudakis, O. B. Wright, O. Matsuda
Physical Review B, 01 Jun. 2021
Scientific journal

Optical generation and detection of gigahertz shear acoustic waves in solids assisted by a metallic diffraction grating
Osamu Matsuda, Kandai Tsutsui, Gwenaëlle Vaudel, Thomas Pezeril, Kentaro Fujita, Vitalyi Gusev
Physical Review B, 22 Jun. 2020, [Peer-reviewed]
Scientific journal

Wave-canceling acoustic metarod architected with single material building blocks
Akira Ogasawara, Kentaro Fujita, Motonobu Tomoda, Osamu Matsuda, Oliver B. Wright
Applied Physics Letters, 116, 24, 241904, 241904, {AIP} Publishing, 15 Jun. 2020, [Peer-reviewed]
Scientific journal

Giant extraordinary transmission of acoustic waves through a nanowire
T. Devaux, H. Tozawa, P. H. Otsuka, S. Mezil, M. Tomoda, O. Matsuda, E. Bok, S. H. Lee, O. B. Wright
Science Advances, 6, 10, American Association for the Advancement of Science ({AAAS}), 04 Mar. 2020, [Peer-reviewed]
Scientific journal

Perfect acoustic bandgap metabeam based on a quadruple-mode resonator array
Kentaro Fujita, Motonobu Tomoda, Oliver B. Wright, Osamu Matsuda
Applied Physics Letters, 115, 8, 081905-1, 5, 19 Aug. 2019, [Peer-reviewed]
English, Scientific journal

Confinement of acoustic fields in a honeycomb phononic crystal slab
Paul H. Otsuka, Sorasak Danworaphong, Istvan Veres, Oliver B. Wright, Ryota Chinbe, Motonobu Tomoda, Yukihiro Tanaka, Sihan H. Kim, Osamu Matsuda, Heonsu S. Jeon
Proceeding - 5th International Conference on Engineering, Applied Sciences and Technology, ICEAST 2019, Institute of Electrical and Electronics Engineers Inc., 01 Jul. 2019
English, International conference proceedings, We demonstrate the nement of acoustic waves in a microscopic phononic crystal slab consisting of a honeycomb array of holes in silicon. The acoustic field is measured on the sample surface at frequencies up to 1GHz by means of an ultrafast optical technique. Using temporal Fourier transforms, the confinement is shown to depend on frequency, and a phononic band gap is identified. Finite element simulations are performed and used to analyze the results.

Imaging gigahertz zero-group-velocity Lamb waves
Qingnan Xie, Sylvain Mezil, Paul H. Otsuka, Motonobu Tomoda, Jérôme Laurent, Osamu Matsuda, Zhonghua Shen, Oliver B. Wright
Nature Communications, 10, 1, 2228-1, 12, Springer Science and Business Media {LLC}, 20 May 2019, [Peer-reviewed]
English, Scientific journal

Time-resolved imaging of GHz acoustic waves in two-dimensional phononic crystals with an arbitrary-frequency technique
Osamu Matsuda, Hiroki Muramoto, Hiroki Nishita, Kentaro Fujita, Motonobu Tomoda, Oliver B. Wright
Proceedings of the International Congress on Acoustics, 2019-, 8209, 8211, International Commission for Acoustics (ICA), 2019
English, International conference proceedings, By irradiating a medium with picosecond light pulses one can generate GHz surface acoustic waves. Their propagation can be monitored in the time domain with delayed probe light pulses. In addition, by spatially scanning the probe light focusing position, it is possible to monitor the spatiotemporal variation of the acoustic field. This can be used to study acoustic properties such as the dispersion relation of the surface acoustic waves in a medium. For such measurements, a periodic source of light pulses with a repetition rate of around 80 MHz is usually used, and so the frequency of the generated acoustic waves is limited to integer multiples of the repetition rate. We recently developed a technique to generate and detect arbitrary acoustic frequency components through the intensity modulation of the excitation, i.e. pump, light pulse train. In this paper, this arbitrary-frequency imaging technique is applied to study the acoustic properties of two- dimensional phononic crystals. The sample contains a square array of micron-scale holes on a Si substrate, and exhibits a phononic band gap around 0.5 GHz. We will present experimental results concerning acoustic wave propagation at frequencies around the phononic band gap.

Time-domain imaging of gigahertz surface waves on an acoustic metamaterial
Osamu Matsuda
New Journal of Physics, 20, 1, 013026-1, 12, Institute of Physics Publishing, 22 Jan. 2018, [Peer-reviewed]
English, Scientific journal, We extend time-domain imaging in acoustic metamaterials to gigahertz frequencies. Using a sample consisting of a regular array of ∼1 μm diameter silica microspheres forming a two-dimensional triangular lattice on a substrate, we implement an ultrafast technique to probe surface acoustic wave propagation inside the metamaterial area and incident on the metamaterial from a region containing no microspheres, which reveals the acoustic metamaterial dispersion, the presence of band gaps and the acoustic transmission properties of the interface. A theoretical model of this locally resonant metamaterial based on normal and shear-rotational resonances of the spheres fits the data well. Using this model, we show analytically how the sphere elastic coupling parameters influence the gap widths.

Time-domain Brillouin scattering assisted by diffraction gratings
Matsuda, O., Pezeril, T., Chaban, I., Fujita, K., Gusev, V.
Physical Review B, 97, 6, 064301-1, 11, American Physical Society, 2018, [Peer-reviewed]
English, Scientific journal, Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.

Active chiral control of GHz acoustic whispering-gallery modes
Sylvain Mezil, Kentaro Fujita, Paul H. Otsuka, Motonobu Tomoda, Matt Clark, Oliver B. Wright, Osamu Matsuda
Applied Physics Letters, 111, 14, 144103, 144103, {AIP} Publishing, 02 Oct. 2017, [Peer-reviewed]
English, Scientific journal, We selectively generate chiral surface-acoustic whispering-gallery modes in the gigahertz range on a microscopic disk by means of an ultrafast time-domain technique incorporating a spatial light modulator. Active chiral control is achieved by making use of an optical pump spatial profile in the form of a semicircular arc, positioned on the sample to break the symmetry of clockwise-and counterclockwise-propagating modes. Spatiotemporal Fourier transforms of the interferometrically monitored two-dimensional acoustic fields measured to micron resolution allow individual chiral modes and their azimuthal mode order, both positive and negative, to be distinguished. In particular, for modes with 15-fold rotational symmetry, we demonstrate ultrafast chiral control of surface acoustic waves in a micro-acoustic system with picosecond temporal resolution. Applications include nondestructive testing and surface acoustic wave devices. Published by AIP Publishing.

Gigahertz optomechanical modulation by split-ring-resonator nanophotonic meta-atom arrays
Osamu Matsuda
Nano Letters, 17, 11, 6684, 6689, AMER CHEMICAL SOC, 15 Sep. 2017, [Peer-reviewed]
English, Scientific journal, Using polarization-resolved transient reflection spectroscopy, we investigate a metasurface consisting of coherently vibrating nanophotonic U-shaped split-ring meta-atoms that exhibit colocalized optical and mechanical resonances. With an array of these resonators formed of gold on glass, essentially miniature tuning forks, we monitor the visible-pump induced gigahertz oscillations in reflected infrared light intensity to probe the multimodal vibrational response. Numerical simulations of the associated transient deformations and strain fields elucidate the complex nanomechanical dynamics contributing to the ultrafast optical modulation and point to the role of acousto-plasmonic interactions through the opening and closing motion of the SRR gaps as the dominant effect. Applications include ultrafast acoustooptic modulator design and sensing.

Elucidating gigahertz acoustic modulation of extraordinary optical transmission through a two-dimensional array of nano-holes
Ulbricht, R., Sakuma, H., Imade, Y., Otsuka, P. H., Tomoda, M., Matsuda, O., Kim, H., Park, G. W., Wright, O. B.
Applied Physics Letters, 110, 9, 091910-1, 5, AMER INST PHYSICS, 2017, [Peer-reviewed]
English, Scientific journal, The ultrafast modulation of light transmitted by a metamaterial making up an extraordinary optical transmission geometry is investigated by means of optical pump-probe spectroscopy. Using a sample consisting of a lattice of square nano-holes in a gold film on a glass substrate, we monitor the high-frequency oscillations in the intensity of transmitted infrared light. A variety of gigahertz acoustic modes, involving the opening and shutting motion of the holes as well as the straining of the glass substrate below the holes, are revealed to be active in the optical modulation. Numerical simulations of the transient deformations and strain fields elucidate the nature of the vibrational modes contributing most strongly to the variations in optical transmission, and point to the hole-area modulation as the dominant effect. Potential applications include ultrafast acousto-optic modulators. Published by AIP Publishing.

Optical tracking of picosecond coherent phonon pulse focusing inside a sub-micron object.
Dehoux T, Ishikawa K, Otsuka PH, Tomoda M, Matsuda O, Fujiwara M, Takeuchi S, Veres IA, Gusev VE, Wright OB
Light, science & applications, 5, 5, e16082, May 2016, [Peer-reviewed]
English, Scientific journal

Theory for optical detection of picosecond shear acoustic gratings
Kouyate, Mansour, Pezeril, Thomas, Gusev, Vitalyi, Matsuda, Osamu
Journal of the Optical Society of America B-Optical Physics, 33, 12, 2634, 2648, OPTICAL SOC AMER, 2016, [Peer-reviewed]
English, Scientific journal, A theoretical formalism describing the heterodyne detection of plane inhomogeneous shear acoustic waves by probe laser-induced gratings is developed. An inhomogeneous plane shear acoustic wave is a purely shear wave with a plane phase front and mechanical displacement vector, which is sinusoidally spatially modulated in magnitude. It could be generated by laser-induced gratings and could be useful for the acoustic testing of sub-micrometer thick membranes and coatings in the gigahertz frequency range. The theory reveals the potential advantages and disadvantages of this wave application in non-destructive testing of materials and fundamental research from the point of view of the feasibility of their experimental detection. (C) 2016 Optical Society of America

Optical tracking of picosecond coherent phonon pulse focusing inside a sub-micron object
Dehoux, Thomas, Ishikawa, Kenichi, Otsuka, Paul H., Tomoda, Motonobu, Matsuda, Osamu, Fujiwara, Masazumi, Takeuchi, Shigeki, Veres, Istvan A., Gusev, Vitalyi E., Wright, Oliver B.
Light-Science & Applications, 5, E16082-1, 7, CHINESE ACAD SCIENCES, CHANGCHUN INST OPTICS FINE MECHANICS AND PHYSICS, 2016, [Peer-reviewed]
English, Scientific journal, By means of an ultrafast optical technique, we track focused gigahertz coherent phonon pulses in objects down to sub-micron in size. Infrared light pulses illuminating the surface of a single metal-coated silica fibre generate longitudinal-phonon wave packets. Reflection of visible probe light pulses from the fibre surface allows the vibrational modes of the fibre to be detected, and Brillouin optical scattering of partially transmitted light pulses allows the acoustic wavefronts inside the transparent fibre to be continuously monitored. We thereby probe acoustic focusing in the time domain resulting from generation at the curved fibre surface. An analytical model, supported by three-dimensional simulations, suggests that we have followed the focusing of the acoustic beam down to a similar to 150-nm diameter waist inside the fibre. This work significantly narrows the lateral resolution for focusing of picosecond acoustic pulses, normally limited by the diffraction limit of focused optical pulses to similar to 1 mu m, and thereby opens up a new range of possibilities including nanoscale acoustic microscopy and nanoscale computed tomography.

Extraordinary transmission of gigahertz surface acoustic waves
Mezil, Sylvain, Chonan, Kazuki, Otsuka, Paul H., Tomoda, Motonobu, Matsuda, Osamu, Lee, Sam H., Wright, Oliver B.
Scientific Reports, 6, 33380-1, 11, NATURE PUBLISHING GROUP, 2016, [Peer-reviewed]
English, Scientific journal, Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths lambda similar to 3-50 mu m, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one-and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to similar to 23 and similar to 8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.

Optical characterization of phononic crystals in the time domain
Osamu Matsuda, Oliver B. Wright
Phononic Crystals: Fundamentals and Applications, 192, 213, Springer New York, 28 Jul. 2015, [Peer-reviewed]
English, In book

18aCF-13 Time-resolved two-dimensional imaging of sub-GHz acoustic whispering gallery modes at arbitrary frequencies
Matsuda Osamu, Mezil Sylvain, Otsuka Paul H., Kaneko Shogo, Wright Oliver B., Tomoda Motonobu
Meeting Abstracts of the Physical Society of Japan, 70, 1253, 1253, The Physical Society of Japan (JPS), 2015
Japanese

Wideband fluorescence-based thermometry by neural network recognition: Photothermal application with 10 ns time resolution
Liu, Liwang, Zhong, Kuo, Munro, Troy, Alvarado, Salvador, Cote, Renaud, Creten, Sebastiaan, Fron, Eduard, Ban, Heng, Van der Auweraer, Mark, Roozen, N. B., Matsuda, Osamu, Glorieux, Christ
Journal of Applied Physics, 118, 18, 184906-1, 12l, AMER INST PHYSICS, 2015, [Peer-reviewed]
English, Scientific journal, Neural network recognition of features of the fluorescence spectrum of a thermosensitive probe is exploited in order to achieve fluorescence-based thermometry with an accuracy of 200mK with 100MHz bandwidth, and with high robustness against fluctuations of the probe laser intensity used. The concept is implemented on a rhodamine B dyed mixture of copper chloride and glycerol, and the temperature dependent fluorescence is investigated in the temperature range between 234K and 311 K. The spatial dependence of the calibrated amplitude and phase of photothermally induced temperature oscillations along the axis of the excitation laser are determined at different modulation frequencies. The spatial and frequency dependence of the extracted temperature signals is well fitted by a 1D multi-layer thermal diffusion model. In a time domain implementation of the approach, the gradual temperature rise due to the accumulation of the DC component of the heat flux supplied by repetitive laser pulses as well the immediate transient temperature evolution after each single pulse is extracted from acquired temporal sequences of fluorescence spectra induced by a CW green laser. A stroboscopic implementation of fluorescence thermometry, using a pulsed fluorescence evoking probe laser, is shown to achieve remote detection of temperature changes with a time resolution of 10 ns. (C) 2015 AIP Publishing LLC.

Watching surface waves in phononic crystals
Wright, Oliver B., Matsuda, Osamu
Philosophical Transactions of the Royal Society a-Mathematical Physical and Engineering Sciences, 373, 2049, 20140364-1, 18, ROYAL SOC, 2015, [Peer-reviewed]
English, Scientific journal, In this paper, we review results obtained by ultrafast imaging of gigahertz surface acoustic waves in surface phononic crystals with one- and two-dimensional periodicities. By use of quasi-point-source optical excitation, we show how, from a series of images that form a movie of the travelling waves, the dispersion relation of the acoustic modes, their corresponding mode patterns and the position and widths of phonon stop bands can be obtained by temporal and spatio-temporal Fourier analysis. We further demonstrate how one can follow the temporal evolution of phononic eigenstates in k-space using data from phononic-crystal waveguides as an example. (C) 2015 The Author(s) Published by the Royal Society. All rights reserved.

Time-Resolved Gigahertz Acoustic Wave Imaging at Arbitrary Frequencies
Matsuda, Osamu, Kaneko, Shogo, Wright, Oliver B., Tomoda, Motonobu
Ieee Transactions on Ultrasonics Ferroelectrics and Frequency Control, 62, 3, 584, 595, IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2015, [Peer-reviewed]
English, Scientific journal, We describe a way to generate and detect arbitrary frequency components in time-resolved surface acoustic wave imaging based on optical pumping and probing with a periodic light source. The detailed theory of the technique, based on beam modulation and Fourier analysis, for a variety of possible experimental configurations is presented, followed by experimental data for a glass substrate covered with a thin gold film. We show how the acoustic dispersion relation can be obtained to arbitrary frequency resolution, not limited by the laser pulse repetition rate.

Three-dimensional imaging of biological cells with picosecond ultrasonics
Danworaphong, Sorasak, Tomoda, Motonobu, Matsumoto, Yuki, Matsuda, Osamu, Ohashi, Toshiro, Watanabe, Hiromu, Nagayama, Masafumi, Gohara, Kazutoshi, Otsuka, Paul H., Wright, Oliver B.
Applied Physics Letters, 106, 16, 163701-1, 5, AMER INST PHYSICS, 2015, [Peer-reviewed]
English, Scientific journal, We use picosecond ultrasonics to image animal cells in vitro-a bovine aortic endothelial cell and a mouse adipose cell-fixed to Ti-coated sapphire. Tightly focused ultrashort laser pulses generate and detect GHz acoustic pulses, allowing three-dimensional imaging (x, y, and t) of the ultrasonic propagation in the cells with similar to 1 mu m lateral and similar to 150 nm depth resolutions. Time-frequency representations of the continuous-wavelet-transform amplitude of the optical reflectivity variations inside and outside the cells show GHz Brillouin oscillations, allowing the average sound velocities of the cells and their ultrasonic attenuation to be obtained as well as the average bulk moduli. (C) 2015 AIP Publishing LLC.

Imaging of transient surface acoustic waves by full-field photorefractive interferometry
Xiong, Jichuan, Xu, Xiaodong, Glorieux, Christ, Matsuda, Osamu, Cheng, Liping
Review of Scientific Instruments, 86, 5, 053107-1, 8, AMER INST PHYSICS, 2015, [Peer-reviewed]
English, Scientific journal, A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm x 17 mm area on an aluminum plate was visualized with 520 x 696 pixels of the CCD sensor, yielding a spatial resolution of 33 mu m. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz. (C) 2015 AIP Publishing LLC.

Imaging arbitrary acoustic whispering-gallery modes in the gigahertz range with ultrashort light pulses
Mezil, Sylvain, Otsuka, Paul H., Kaneko, Shogo, Wright, Oliver B., Tomoda, Motonobu, Matsuda, Osamu
Optics Letters, 40, 10, 2157, 2160, OPTICAL SOC AMER, 2015, [Peer-reviewed]
English, Scientific journal, Using an ultrafast optical technique with enhanced frequency control, we image surface-acoustic whispering-gallery-like modes in a microscopic disk at various frequencies up to 1 gigahertz (GHz), allowing experimental determination of their dispersion. This is made possible by intensity-modulated optical pumping and probing with a periodic femtosecond light source. Spatiotemporal Fourier transforms of the two-dimensional acoustic fields measured to micron resolution allow us to isolate individual whispering-gallery modes of first and second radial order as well as their mode patterns and Q factors to unprecedented frequency resolution. We thereby demonstrate arbitrary-frequency ultrafast control and imaging of a micro-acoustic system with an optical time-resolved technique. Applications include quality control of surface acoustic wave filters in telecommunications. (C) 2015 Optical Society of America

Fundamentals of picosecond laser ultrasonics
Matsuda, Osamu, Larciprete, Maria Cristina, Li Voti, Roberto, Wright, Oliver B.
Ultrasonics, 56, 3, 20, ELSEVIER SCIENCE BV, 2015, [Peer-reviewed]
English, Scientific journal, The aim of this article is to provide an introduction to picosecond laser ultrasonics, a means by which gigahertz-terahertz ultrasonic waves can be generated and detected by ultrashort light pulses. This method can be used to characterize materials with nanometer spatial resolution. With reference to key experiments, we first review the theoretical background for normal-incidence optical detection of longitudinal acoustic waves in opaque single-layer isotropic thin films. The theory is extended to handle isotropic multilayer samples, and is again compared to experiment. We then review applications to anisotropic samples, including oblique-incidence optical probing, and treat the generation and detection of shear waves. Solids including metals and semiconductors are mainly discussed, although liquids are briefly mentioned. (C) 2014 Elsevier B.V. All rights reserved.

Effect of excitation point on surface phonon fields in phononic crystals in real- and k-space
Otsuka, P. H., Chinbe, R., Tomoda, M., Matsuda, O., Veres, I. A., Lee, J. -H., Yoon, J. -B., Wright, O. B.
Journal of Applied Physics, 117, 24, 245308-1, 6, AMER INST PHYSICS, 2015, [Peer-reviewed]
English, Scientific journal, We investigate surface phonon propagation in a triangular-lattice phononic crystal of microscopic holes in a gold-coated polymer by time-resolved two-dimensional imaging and by finite-element simulations at sub-gigahertz frequencies. The simulations allow the effects of exciting different points in the crystal lattice to be studied in real space, and also in k-space by spatiotemporal Fourier analysis. The acoustic field in a sub-surface plane below the reach of the holes is also revealed in real-and k-spaces. In addition, we demonstrate pitfalls in the analysis of k-space data when searching for the presence of band gaps. Applications include surface-acoustic wave filter quality control. (C) 2015 AIP Publishing LLC.

Nanoscale mechanical contacts mapped by ultrashort time-scale electron transport
Tomoda, M., Dehoux, T., Iwasaki, Y., Matsuda, O., Gusev, V. E., Wright, O. B.
Scientific Reports, 4, 4790-1, 5, NATURE PUBLISHING GROUP, 2014, [Peer-reviewed]
English, Scientific journal, Mechanical contacts are crucial to systems in engineering, electronics and biology. The microscopic nature of the contacting surfaces determines how they mesh on the nanoscale. There is thus much interest in methods that can map the actual area of two surfaces in contact-the real contact area during the loading or unloading phases. We address this problem using an ultrafast optical technique to generate non-equilibrium electrons that diffuse across a nanoscale mechanical contact between two thin gold films deposited on sapphire. We image this process in the contact and near-contact regions to micron resolution in situ using transient optical reflectivity changes on femtosecond time scales. By use of a model of the ultrashort-time electron dynamics, we account for an up to similar to 40%dropin the transient optical reflectivity change on contact. We thereby show how the real contact area of a nanoscale contact can be mapped. Applications include the probing of microelectronic mechanical devices.

A method for the frequency control in time-resolved two-dimensional gigahertz surface acoustic wave imaging
Kaneko, S., Tomoda, M., Matsuda, O.
Aip Advances, 4, 1, 017124-1, 8, AMER INST PHYSICS, 2014, [Peer-reviewed]
English, Scientific journal, We describe an extension of the time-resolved two-dimensional gigahertz surface acoustic wave imaging based on the optical pump-probe technique with periodic light source at a fixed repetition frequency. Usually such imaging measurement may generate and detect acoustic waves with their frequencies only at or near the integer multiples of the repetition frequency. Here we propose a method which utilizes the amplitude modulation of the excitation pulse train to modify the generation frequency free from the mentioned limitation, and allows for the first time the discrimination of the resulted upper- and lower-side-band frequency components in the detection. The validity of the method is demonstrated in a simple measurement on an isotropic glass plate covered by a metal thin film to extract the dispersion curves of the surface acoustic waves. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

Imaging acoustic waves in microscopic wedges
Tomoda, Motonobu, Matsueda, Shinnosuke, Otsuka, Paul H., Matsuda, Osamu, Veres, Istvan A., Gusev, Vitalyi E., Wright, Oliver B.
New Journal of Physics, 16, 103029-1, 9, IOP PUBLISHING LTD, 2014, [Peer-reviewed]
English, Scientific journal, Using an ultrafast optical technique we image near-gigahertz flexural acoustic waves propagating in a thin gold wedge deposited on an ultrathin silicon nitride slab. Temporal Fourier transforms of the imaged data in two dimensions allow individual frequencies to be accessed. The wave fronts associated with antisymmetric Lamb waves bend towards the thin end of the wedge. This behaviour is mimicked with an analytical model based on sections of a linear wedge. We also conduct numerical simulations which show good agreement with the experimental results.

Ultrafast ellipsometric interferometry for direct detection of coherent phonon strain pulse profiles
Matsuda, O., Tomoda, M., Tachizaki, T., Koiwa, S., Ono, A., Aoki, K., Beardsley, R. P., Wright, O. B.
Journal of the Optical Society of America B-Optical Physics, 30, 7, 1911, 1921, OPTICAL SOC AMER, 2013, [Peer-reviewed]
English, Scientific journal, We describe an ultrafast optical technique to quantitatively detect picosecond ultrasonic displacements of solid surfaces, thus giving access to the longitudinal strain pulse shape. Transient optical reflectance changes recorded at oblique optical incidence with a common-path interferometric configuration based on ultrafast ellipsometry monitor gigahertz coherent phonon pulses. We demonstrate for a tungsten film the quantitative extraction of the strain pulse shape free of distortions arising from the photoelastic effect, and analyze the results with the two-temperature model to obtain the value g approximate to 3 x 10(17) Wm(-3) K-1 for the electron-phonon coupling constant. Analysis of the data also reveals a thermo-optic contribution. (C) 2013 Optical Society of America

Mapping gigahertz vibrations in a plasmonic-phononic crystal
Kelf, T. A., Hoshii, W., Otsuka, P. H., Sakuma, H., Veres, I. A., Cole, R. M., Mahajan, S., Baumberg, J. J., Tomoda, M., Matsuda, O., Wright, O. B.
New Journal of Physics, 15, 023013-1, 14, 2013, [Peer-reviewed]
English, Scientific journal, We image the gigahertz vibrational modes of a plasmonic-phononic crystal at sub-micron resolution by means of an ultrafast optical technique, using a triangular array of spherical gold nanovoids as a sample. Light is strongly coupled to the plasmonic modes, which interact with the gigahertz phonons by a process akin to surface-enhanced stimulated Brillouin scattering. A marked enhancement in the observed optical reflectivity change at the centre of a void on phononic resonance is likely to be caused by this mechanism. By comparison with numerical simulations of the vibrational field, we identify resonant breathing deformations of the voids and elucidate the corresponding mode shapes. We thus establish scanned optomechanical probing of periodic plasmonic-phononic structures as a new means of investigating their coupled excitations on the nanoscale. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Complex band structures of two dimensional phononic crystals: Analysis by the finite element method
Veres, I. A., Berer, T., Matsuda, O.
Journal of Applied Physics, 114, 8, 083519-1, 11, 2013, [Peer-reviewed]
English, Scientific journal, In this work, the calculation of complex band structures of two-dimensional bulk phononic crystals (2DPCs) is discussed by the finite element method. A modification of the classical ω (k) approach - calculating the unknown frequencies for a real wave number - is modified to a k (ω) solution, which allows the evaluation of complex wave numbers for real frequencies. The dispersion relation of a 2DPC in a square lattice is presented and it is shown that the problem reduces to a polynomial eigenvalue problem with quadratic and quartic eigenvalue problems in the Γ - X - M - Γ directions. The developed method is applied for solid-vacuum PCs made of isotropic materials consisting cylindrical holes. Complex dispersion diagrams are calculated with various Poisson's ratios and the mode shapes of the propagating and the evanescent modes are presented. The significance of the complex bands is discussed. © 2013 AIP Publishing LLC.

Bulk and surface acoustic wave phenomena in crystals: Observation and interpretation
Every, A. G., Maznev, A. A., Grill, W., Pluta, M., Comins, J. D., Wright, O. B., Matsuda, O., Sachse, W., Wolfe, J. P.
Wave Motion, 50, 8, 1197, 1217, ELSEVIER SCIENCE BV, 2013, [Peer-reviewed]
English, Scientific journal, Crystal acoustics is a field that has engaged the attention of theoreticians and experimentalists alike for decades and more. Many striking effects have been revealed, and elegant analytical techniques applied to their interpretation. This article is oriented towards the experimental aspects of the field and the interpretation of the phenomena that have been observed. Particular attention is given to reviewing the techniques that have probed the intricacy of acoustic wave propagation in crystals, including phonon imaging, laser- and capillary-fracture-generated ultrasound, transmission acoustic microscopy and surface Brillouin scattering, and a selection of results obtained with these techniques is presented. Some of these studies pertain to bulk waves and others to surface acoustic waves. The interpretation of far-field observations is carried out within the ray approximation, and elastodynamic Green's functions are invoked in the interpretation of near-field results. Extensive use is made of the acoustic-slowness and wave surfaces, in particular features such as acoustic axes, with their attendant polarization singularities, and folds in the wave surface. (C) 2013 Elsevier B.V. All rights reserved.

Broadband evolution of phononic-crystal-waveguide eigenstates in real- and k-spaces
Otsuka, P. H., Nanri, K., Matsuda, O., Tomoda, M., Profunser, D. M., Veres, I. A., Danworaphong, S., Khelif, A., Benchabane, S., Laude, V., Wright, O. B.
Scientific Reports, 3, 3351-1, 5, 2013, [Peer-reviewed]
English, Scientific journal, Control of sound in phononic band-gap structures promises novel control and guiding mechanisms. Designs in photonic systems were quickly matched in phononics, and rows of defects in phononic crystals were shown to guide sound waves effectively. The vast majority of work in such phononic guiding has been in the frequency domain, because of the importance of the phononic dispersion relation in governing acoustic confinement in waveguides. However, frequency-domain studies miss vital information concerning the phase of the acoustic field and eigenstate coupling. Using a wide range of wavevectors k, we implement an ultrafast technique to probe the wave field evolution in straight and L-shaped phononic crystal surface-phonon waveguides in real- and k-space in two spatial dimensions, thus revealing the eigenstate-energy redistribution processes and the coupling between different frequency-degenerate eigenstates. Such use of k-t space is a first in acoustics, and should have other interesting applications such as acoustic-metamaterial characterization.

Watching GHZ ultrasonic waves in K-space　　　　　　　　　　　　　　　
Oliver B. Wright, Paul H. Otsuka, Keisuke Nanri, Motonobu Tomoda, Osamu Matsuda, Dieter M. Profunser, Istvan A. Veres, Sorasak Danworaphong, Abdelkrim Khelif, Sarah Benchabane, Vincent Laude
20th International Congress on Sound and Vibration 2013, ICSV 2013, 3, 2638, 2639, International Institute of Acoustics and Vibrations, 2013
English, International conference proceedings, Waveguide devices for Controlling the path of propagation of surface acoustic waves can be created by introducing defects in a phononic crystal. Such waveguides show more complex dispersion than conventional waveguides, and are useful in applications such as signal processing. Here we present spatio-temporal Fourier analysis of real-time imaging and simulation of laser-induced surface acoustic waves at frequencies up to ∼ 1 GHz in phononic crystal waveguides formed by machining microscopic holes in a silicon slab. In particular we analyse our results as movies in k-space, revealing the effects of diffraction, reflection, waveguiding and attenuation in a particularly simple way.

Complexity of band structures: Finite element calculation of complex band structures for one and two dimensional phononic crystals
Istvan A. Veres, Thomas Berer, Osamu Matsuda
IEEE International Ultrasonics Symposium, IUS, 729, 732, 2013, [Peer-reviewed]
English, International conference proceedings, The calculation of complex band structures for surface gratings (one dimensional phononic crystals) and for two dimensional phononic crystals is discussed in the presented paper. We show an extension of the finite element method and the semi-analytical finite element method based on the dynamic condensation to achieve this aim. Complex band structures are particularly important for surface gratings, since the folded surface waves become evanescent beyond the sound cone. This behavior and the complex interconnections between the real propagating modes are discussed. The presence of an evanescent mode within the complete stop band is shown for surface gratings. This describes the spatial decay of the elastic waves inside the stop band. The presented method is extended for two dimensional phononic crystals with square lattices whereby the different orientations of the wave vector lead to polynomial eigenvalue problems including quadratic and quartic eigenvalue problems. © 2013 IEEE.

Thermoelastic Model for Impulsive Stimulated Scattering Monitoring the Evolution from Capillary to Rayleigh Type Wave Propagation on the Surface of Viscoelastic Materials Throughout the Glass Transition
Sermeus, J., Matsuda, O., Salenbien, R., Verstraeten, B., Fivez, J., Glorieux, C.
International Journal of Thermophysics, 33, 10-11, 2145, 2158, SPRINGER/PLENUM PUBLISHERS, 2012, [Peer-reviewed]
English, Scientific journal, In recent decades, the impulsive stimulated scattering (ISS) method, which is based on photothermal and photoacoustic phenomena, has been successfully used to simultaneously investigate the thermal and elastic properties in a four-wave mixing configuration, both in transmission in semitransparent materials and on reflecting surfaces of solids. In this report, an extension of the technique is proposed to study a laser-induced thermoelastic response at the free surface of glass-forming liquids. The employed all-optical configuration allows extraction of information about the acoustic shear modulus in the MHz frequency range, and hence is complementary to the classical ISS configuration in the transmission mode, which is suitable to study the relaxation of the longitudinal acoustic modulus, and to another earlier reported ISS configuration, which is exciting and probing laser-induced thermoelastic phenomena at a liquid-solid interface. A theoretical model is presented and numerically illustrated for the glass transition of glycerol, and experimentally validated for water at room temperature.

Point source in a phononic grating: stop bands give rise to phonon-focusing caustics
Veres, I. A., Profunser, D. M., Maznev, A. A., Every, A. G., Matsuda, O., Wright, O. B.
New Journal of Physics, 14, 123015-1, 28, IOP PUBLISHING LTD, 2012, [Peer-reviewed]
English, Scientific journal, We use locally-excited gigahertz surface phonon wavepackets in microscopic line structures of different pitches to reveal profound anisotropy in the radiation pattern of a point source in a grating. Time-domain data obtained by an ultrafast optical imaging technique and by numerical simulations are Fourier transformed to obtain frequency-filtered real-space acoustic field patterns and k-space phononic band structure. The numerically-obtained k-space images are processed to reveal an intriguing double-horn structure in the lowest-order group-velocity surface, which explains the observed non-propagation sectors bounded by caustics, noted at frequencies above the bottom of the first stop band. We account for these phonon-focusing effects, analogous to collimation effects previously observed in two-and three-dimensional lattices, with a simple analytical model of the band structure based on a plane wave expansion. As the frequency is increased, a transition to dominant waveguiding effects along the lines is also documented.

Vibrational modes of GaAs hexagonal nanopillar arrays studied with ultrashort optical pulses
Sakuma, Hirotaka, Tomoda, Motonobu, Otsuka, Paul H., Matsuda, Osamu, Wright, Oliver B., Fukui, Takashi, Tomioka, Katsuhiro, Veres, Istvan A.
Applied Physics Letters, 100, 13, 131902-1, 3, AMER INST PHYSICS, 2012, [Peer-reviewed]
English, Scientific journal, We investigate the vibrational modes of a triangular array of anisotropic, hexagonal GaAs nanopillars on a GaAs substrate through ultrafast changes in optical reflectivity. By comparison with simulations, we identify GHz resonances, mode shapes, and damping. In addition, by varying the pillar diameter, height, and pitch, we distinguish collective and localized modes. A proper understanding of substrate-attached nanostructure dynamics will lead to better characterization of nanosensors based on perturbations to vibrational resonances. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3696380]

Focusing and subwavelength imaging of surface acoustic waves in a solid-air phononic crystal
Veres, I. A., Berer, T., Matsuda, O., Burgholzer, P.
Journal of Applied Physics, 112, 5, 053504-1, 7, AMER INST PHYSICS, 2012, [Peer-reviewed]
English, Scientific journal, Focusing and subwavelength imaging of surface acoustic waves (SAWs) through a phononic crystal flat lens are discussed in the presented work. Experimental and numerical wave fields are obtained in the time-domain by an optical technique and by numerical simulations. Spatial distributions of the acoustic field are accessed using a temporal Fourier transform. The revealed focusing of the elastic waves in the first band of the crystal is governed by the concave equifrequency contour of the leaky-Rayleigh wave. The spatial distributions of the experimental and numerical acoustic fields also unfold subwavelength imaging of SAWs. Numerical simulations show that the imaging quality can be improved by embedding the flat lens into a medium with higher wave velocity. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747931]

Dynamic visualization of surface phonons in phononic crystals
Wright, Oliver B., Veres, Istvan A., Profunser, Dieter M., Matsuda, Osamu, Culshaw, Brian, Lang, Udo
Chinese Journal of Physics, 49, 1, 16, 22, 2011, [Peer-reviewed]
English, Scientific journal

Real-time imaging of acoustic rectification
Danworaphong, S., Kelf, T. A., Matsuda, O., Tomoda, M., Tanaka, Y., Nishiguchi, N., Wright, O. B., Nishijima, Y., Ueno, K., Juodkazis, S., Misawa, H.
Applied Physics Letters, 99, 20, 201910-1, 3, AMER INST PHYSICS, 2011, [Peer-reviewed]
English, Scientific journal, We image gigahertz surface acoustic waves normally incident on a microscopic linear array of triangular holes-a generic "acoustic diode" geometry-with a real-time ultrafast optical technique. Spatiotemporal Fourier transforms reveal wave diffraction orders in k-space. Squared amplitude reflection and transmission coefficients for incidence on both sides of the array are evaluated and compared with numerical simulations. We thereby directly demonstrate acoustic rectification with an asymmetric structure. (C) 2011 American Institute of Physics. [doi:10.1063/1.3662930]

Ultrafast Vibrations of Gold Nanorings
Kelf, T. A., Tanaka, Y., Matsuda, O., Larsson, E. M., Sutherland, D. S., Wright, O. B.
Nano Letters, 11, 9, 3893, 3898, AMER CHEMICAL SOC, 2011, [Peer-reviewed]
English, Scientific journal, We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We elucidate the corresponding mode shapes and find that the substrate plays an important role in determining the mode damping. This study demonstrates the need for a plasmonic nano-optics approach to understand the optical excitation and detection mechanisms for the vibrations of plasmonic nanostructures.

Real-time Simulations and Experiments on Surface Acoustic Wave Scattering in Periodic Microstructures
Veres, Istvan A., Profunser, Dieter M., Wright, Oliver B., Matsuda, Osamu, Culshaw, Brian
Chinese Journal of Physics, 49, 1, 534, 541, 2011, [Peer-reviewed]
English, Scientific journal

Mapping the band structure of a surface phononic crystal
Maznev, A. A., Wright, O. B., Matsuda, O.
New Journal of Physics, 13, 013037-1, 11, IOP PUBLISHING LTD, 2011, [Peer-reviewed]
English, Scientific journal, We map the band structure of surface acoustic modes of a periodic array of copper lines embedded in a SiO2 film on a silicon substrate by means of the laser-induced transient grating technique. A detailed map of the lowest sheet of the omega(k) surface and partial maps of two higher-order sheets are obtained. We discuss the topology of the omega(k) surface and explain how it arises from the Rayleigh and Sezawa modes of the film/substrate system. In the vicinity of the bandgap formed at the Brillouin zone boundary, the first and second dispersion sheets take the form of a saddle and a bowl, respectively, in agreement with a weak perturbation model. The shape of the third dispersion sheet, however, appears to defy expectations based on the perturbation approach. In particular, it contains minima located off the symmetry directions, which implies the existence of zero group velocity modes with an obliquely directed wavevector.

Dynamic imaging of surface acoustic waves in phononic crystals
Oliver B. Wright, Istvan A. Veres, Dieter M. Profunser, Osamu Matsuda, Brian Culshaw, Udo Lang
SMART NANO-MICRO MATERIALS AND DEVICES, 8204, 820425-1, 6, SPIE-INT SOC OPTICAL ENGINEERING, 2011
English, International conference proceedings, Using ultrashort pulsed optical excitation and interferometric detection, we image ultrahigh- frequency surface acoustic waves on two-dimensional (2D) phononic crystals in the time domain. The samples consist of a square lattice of air-filled holes etched in a silicon substrate. Good agreement with time-domain finite element numerical simulations is obtained. The dispersion relation is derived and stop bands are revealed by means of Fourier transforms. The wave fields corresponding to acoustic eigenmodes at specific frequencies are also presented.

Visualization of negative refraction of surface acoustic waves by numerical simulations and experiments
Istvan A. Veres, Bernhard Reitinger, Thomas Berer, Peter Burgholzer, Oliver B. Wright, Osamu Matsuda
2011 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS), 2011 Vol.2, 1312, 1315, IEEE, 2011
English, International conference proceedings, We investigate numerically and experimentally the negative refraction of surface acoustic waves in two-dimensional phononic crystals in the MHz range. We performed high-performance time-domain simulations of propagating broadband surface acoustic waves with the Finite Element Method (FEM) and spatio-temporal imaging by means of pulsed optical excitation and interferometric detection. Experimental and numerical evidence is found for negative refraction from surface wave focusing at particular frequencies after wave propagation through a parallel-sided phononic crystal layer. Obliquely incident plane waves on a phononic crystal were also investigated by numerical simulations. The transmitted waves show a clear shift of the wave front at particular frequencies, providing further evidence for negative refraction of the surface acoustic waves.

Interferometric imaging of surface acoustic waves on a glass sphere
Otsuka, P. H., Matsuda, O., Tomoda, M., Wright, O. B.
Journal of Applied Physics, 108, 12, 123508-1, 5, AMER INST PHYSICS, 2010, [Peer-reviewed]
English, Scientific journal, We use an ultrafast optical pump and probe technique to investigate the propagation of subgigahertz surface acoustic waves on a 1 mm diameter glass sphere with an aluminum coating. A fiber-based pump setup generates the surface waves and a common-path interferometer images them in the time domain over the sphere surface as they pass through the pole opposite the source of excitation. Fourier analysis allows the acoustic spectrum of the acoustic source to be extracted and waves traveling in opposite directions to be isolated. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3517076]

Time resolved imaging of carrier and thermal transport in silicon
Hurley, D. H., Wright, O. B., Matsuda, O., Shinde, S. L.
Journal of Applied Physics, 107, 2, 023521-1, 5, AMER INST PHYSICS, 2010, [Peer-reviewed]
English, Scientific journal, We use ultrashort optical pulses to microscopically image carrier and thermal diffusion in two spatial dimensions in pristine and mechanically polished surfaces of crystalline silicon. By decomposing changes in reflectivity in the latter sample into a transient component that varies with delay time and a steady-state component that varies with pump chopping frequency, the influence of thermal diffusion is isolated from that of carrier diffusion and recombination. Additionally, studies using carrier injection density as a parameter are used to clearly identify the carrier recombination pathway.

Optical generation of surface acoustic waves guided at the linear boundary between two thin films
Maznev, A. A., Kelf, Timothy A., Tomoda, Motonobu, Matsuda, Osamu, Wright, Oliver B.
Journal of Applied Physics, 107, 3, 033521-1, 5, AMER INST PHYSICS, 2010, [Peer-reviewed]
English, Scientific journal, Laser-induced transient grating measurements and ultrafast optical pump-probe imaging of surface acoustic waves near a linear boundary between copper and silica films on a silicon substrate indicate the presence of a boundary-localized mode with a phase velocity slightly below the Rayleigh wave velocity on the copper film. We analyze in detail the dispersion of this localized mode in comparison with that of the Rayleigh waves in the surrounding materials. The existence of the localized mode is ascribed to the nonuniformity of the copper film thickness near its edge resulting from polishing during fabrication.

Acoustic whispering-gallery modes generated and dynamically imaged with ultrashort optical pulses
Tachizaki, Takehiro, Matsuda, Osamu, Maznev, Alex A., Wright, Oliver B.
Physical Review B, 81, 16, 165434-1, 5, AMER PHYSICAL SOC, 2010, [Peer-reviewed]
English, Scientific journal, Broadband coherent surface phonon wave packets up to 1 GHz in a microscopic embedded disk are excited and dynamically imaged with ultrashort optical pulses. We isolate a whispering-gallery-like mode using a technique involving quadrature detection of the out-of-plane surface motion on modulating the optical excitation beam. The eigenmode distribution is obtained from spatiotemporal Fourier transforms and a radial-azimuthal decomposition demonstrates the selective excitation of a mode with 26-fold rotational symmetry and allows an estimate of the cavity Q factor to be made.

Imaging gigahertz surface acoustic waves through the photoelastic effect
Saito, Taiki, Matsuda, Osamu, Tomoda, Motonobu, Wright, Oliver B.
Journal of the Optical Society of America B-Optical Physics, 27, 12, 2632, 2638, OPTICAL SOC AMER, 2010, [Peer-reviewed]
English, Scientific journal, This paper presents experiments and in-depth analysis of the imaging of surface acoustic waves by means of the photoelastic effect. Gigahertz surface acoustic waves, generated by optical pump pulses in a thin gold film on a glass substrate, are imaged in the time domain by monitoring ultrafast changes in optical reflectivity. We demonstrate how images of the in-plane acoustic shear strain component can be obtained by measurements with two different optical probe pulse polarizations incident from the substrate side. (C) 2010 Optical Society of America

Imaging GHz-THz acoustic wave propagation in thin films and microstructures
Osamu Matsuda, Oliver B. Wright
Journal of the Vacuum Society of Japan, 53, 5, 336, 343, 2010, [Peer-reviewed]
Japanese, Scientific journal, Ultrashort light pulses absorbed in a medium generate both bulk and surface acoustic waves: we focus here on imaging the surface waves and on monitoring the bulk acoustic waves that propagate in the depth direction. This is done in the time domain by delayed probe light pulses. For the bulk acoustic waves, the generated frequency ranges up to 1 THz. Some studies concerning the ultrafast electron-phonon relaxation in metal films, high frequency generation in semiconductor quantum wells, and high frequency shear acoustic wave generation and detection are reviewed here. For the surface acoustic waves the generated frequency ranges up to 1 GHz, and time-resolved two-dimensional images of the propagation are obtained with micron lateral spatial resolution. This imaging method is applied to anisotropic crystals and phononic crystals to elucidate their acoustic properties.

Vibrations of microspheres probed with ultrashort optical pulses (vol 34, pg 3740, 2009)
Dehoux, T., Kelf, T. A., Tomoda, M., Matsuda, O., Wright, O. B., Ueno, K., Nishijima, Y., Juodkazis, S., Misawa, H., Tournat, V., Gusev, V. E.
Optics Letters, 35, 7, 940, 940, OSA Publishing, 2010, [Peer-reviewed]
English, Scientific journal

Time resolved acoustic wave imaging for thin films and micro structures in GHz-THz frequency region
Osamu Matsuda, Oliver B. Wright
Journal of the Vaccum Society of Japan, 53, 5, 336, 343, 2010, [Peer-reviewed]
Japanese, Scientific journal

Real-time simulations and experiments on ultrahigh frequency surface waves in micro-structured phononic crystals
VERES Istvan A, PROFUNSER Dieter M, WRIGHT Oliver B, MATSUDA Osamu, LANG Udo
IEEE Int Ultrason Symp, 2009 Vol.2, 1032, 1035, Sep. 2009
English, International conference proceedings

Vibrations of microspheres probed with ultrashort optical pulses
Dehoux, T., Kelf, T. A., Tomoda, M., Matsuda, O., Wright, O. B., Ueno, K., Nishijima, Y., Juodkazis, S., Misawa, H., Tournat, V., Gusev, V. E.
Optics Letters, 34, 23, 3740, 3742, OPTICAL SOC AMER, 2009, [Peer-reviewed]
English, Scientific journal, We use ultrashort optical pulses to excite and detect vibrations of single silica spheres with a diameter of 5 mu m placed at the surface of an acoustically mismatched substrate. In addition to the photoelastic detection of picosecond longitudinal acoustic pulses propagating inside the bulk, we detect gigahertz acoustic resonances of the sphere through probe beam defocusing. The mode frequencies are in close accord with those calculated from the elastic vibrations of a free sphere. We also record a resonant enhancement in the amplitude of specific modes of two touching spheres. (C) 2009 Optical Society of America

Dynamic visualization of surface acoustic waves on a two-dimensional phononic crystal
Profunser, Dieter M., Muramoto, Eiji, Matsuda, Osamu, Wright, Oliver B., Lang, Udo
Physical Review B, 80, 1, 014301-1, 7, AMER PHYSICAL SOC, 2009, [Peer-reviewed]
English, Scientific journal, Surface acoustic wave propagation on a microscopic two-dimensional phononic crystal consisting of a square lattice of holes is imaged in two dimensions and in real time at frequencies up to 1 GHz by means of pulsed ultrashort optical excitation and detection. The acoustic dispersion relation obtained by spatiotemporal Fourier transforms shows the opening of stop bands at the zone boundaries for surface waves traveling parallel to the phononic crystal axes. We detect pronounced Bloch harmonics above the stop band, and reveal the spatial mode distributions at different frequencies. We also observe phonon collimation for frequencies at which the constant-frequency surfaces become square in shape.

Imaging carrier and phonon transport in Si using ultrashort optical pulses
D. H. Hurley, O. B. Wright, O. Matsuda, Brian E. McCandless, Subhash Shinde
ULTRAFAST PHENOMENA IN SEMICONDUCTORS AND NANOSTRUCTURE MATERIALS XIII, 7214, SPIE-INT SOC OPTICAL ENGINEERING, 2009, [Peer-reviewed]
English, International conference proceedings, A series of experiments have been conducted that microscopically image thermal diffusion and surface acoustic phonon propagation within a single crystallite of a polycrystalline Si sample. The experimental approach employs ultrashort optical pulses to generate an electron-hole plasma and a second probe pulse is used to image the evolution of the plasma. By decomposing the signal into a component that varies with delay time and a steady state component that varies with pump modulation frequency, the respective influence of carrier recombination and thermal diffusion are identified. Additionally, the coherent surface acoustic phonon component to the signal is imaged using a Sagnac interferometer to monitor optical phase.

3P1-18　　　　　　　　　　　　　　　
Tomoda Motonobu, Matsueda Shinnosuke, Wright Oliver B, Matsuda Osamu, Nishijima Yoshiaki, Ueno Kosei, Saulius Juodkazis, Misawa Hiroaki
Proceedings of Symposium on Ultrasonic Electronics, 2009
English, Scientific journal

Optical excitation and detection of picosecond acoustic pulses in liquid mercury
Wright, O. B., Perrin, B., Matsuda, O., Gusev, V. E.
Physical Review B, 78, 2, 024303-1, 11, 25 Jul. 2008, [Peer-reviewed]
English, Scientific journal, Ultrashort optical pulses are used to excite and interferometrically detect picosecond longitudinal-acoustic pulses in thin films of liquid mercury sandwiched between sapphire plates. We show that the shape of the strain pulses in the mercury can be directly measured through ultrafast changes in optical reflectivity. By analyzing consecutive acoustic echoes, we derive the dispersion of the ultrasonic attenuation and sound velocity for this liquid at frequencies up to 10 GHz. Significant effects of structural relaxation are observed and are compared to a simple model that indicates the presence of picosecond relaxation times in mercury. © 2008 The American Physical Society.

Coherent shear phonon generation and detection with picosecond laser acoustics
Matsuda, O., Wright, O. B., Hurley, D. H., Gusev, V., Shimizu, K.
Physical Review B, 77, 22, 224110-1, 16, AMER PHYSICAL SOC, 2008, [Peer-reviewed]
English, Scientific journal, Measurements on a film of silica on crystalline zinc using picosecond laser acoustics are theoretically analyzed to quantitatively explain the generation and detection of picosecond shear and longitudinal-acoustic waves. The theory encompasses the scattering of obliquely incident probe light of arbitrary polarization by a depth-dependent anisotropic permittivity modulation in a multilayer, including terms arising from the photoelastic effect, interface displacements, and local rotations. Sound velocities, ultrasonic attenuation, and photoelastic constants are experimentally derived.

Coherent control of gigahertz surface acoustic and bulk phonons using ultrafast optical pulses
Hurley, D. H., Lewis, R., Wright, O. B., Matsuda, O.
Applied Physics Letters, 93, 11, 1131011, 3, AMER INST PHYSICS, 2008, [Peer-reviewed]
English, Scientific journal, We demonstrate the coherent generation and control of gigahertz acoustic phonons with ultrafast optical pulses. Two distinct acoustic phonon modes, a surface acoustic phonon mode and a longitudinal acoustic phonon mode, are generated simultaneously by irradiating nanolithographic absorption gratings on semiconductor substrates. Two material systems are examined: suboptical wavelength aluminum absorption gratings on Si and GaAs substrates. Constructive and complete destructive interference conditions are demonstrated using two pump pulses derived from a single Michelson interferometer. (C) 2008 American Institute of Physics.

Real-time imaging of acoustic waves on a bulk acoustic resonator
Fujikura, Takashi, Matsuda, Osamu, Profunser, Dieter M., Wright, Oliver B., Masson, Jeremy, Ballandras, Sylvain
Applied Physics Letters, 93, 26, 261101-1, 3, AMER INST PHYSICS, 2008, [Peer-reviewed]
English, Scientific journal, Time resolved images of acoustic waves in the 100 MHz-2.2 GHz range are obtained for an electrically excited thin-film bulk acoustic wave resonator by means of an ultrafast optical technique. Electrical pulses, synchronized to ultrashort laser pulses, piezoelectrically excite the device, and synchronous near-infrared laser pulses interferometrically detect surface motion. The frequency dispersion is extracted using spatiotemporal Fourier transforms, revealing both longitudinal and surface acoustic modes.

Optical excitation and detection of picosecond acoustic pulses in liquid mercury
Wright, O. B., Perrin, B., Matsuda, O., Gusev, V. E.
Physical Review B, 78, 2, AMER PHYSICAL SOC, 2008, [Peer-reviewed]
English, Scientific journal, Ultrashort optical pulses are used to excite and interferometrically detect picosecond longitudinal-acoustic pulses in thin films of liquid mercury sandwiched between sapphire plates. We show that the shape of the strain pulses in the mercury can be directly measured through ultrafast changes in optical reflectivity. By analyzing consecutive acoustic echoes, we derive the dispersion of the ultrasonic attenuation and sound velocity for this liquid at frequencies up to 10 GHz. Significant effects of structural relaxation are observed and are compared to a simple model that indicates the presence of picosecond relaxation times in mercury.

Seeking shear waves in liquids with picosecond ultrasonics
M. E. Msall, O. B. Wright, O. Matsuda
12TH INTERNATIONAL CONFERENCE ON PHONON SCATTERING IN CONDENSED MATTER (PHONONS 2007), 92, 012026-1, 4, IOP PUBLISHING LTD, 2007, [Peer-reviewed]
English, International conference proceedings, Picosecond shear acoustic pulses can be generated in solids using ultrashort optical pulses. Here we use this technique to seek high frequency shear waves in water, ethylene glycol and glycerol while simultaneously measuring high frequency longitudinal wave velocity and attenuation. We use a silica thin film on (114) GaAs to generate shear and longitudinal acoustic pulses at frequencies up to similar to 50 GHz by ultrashort pulsed optical excitation. The acoustic pulses are transmitted into adjacent liquids, and are detected through variations in the optical reflectivity. Although we could not detect shear waves in these liquids, we did detect gigahertz longitudinal elastic stiffening.

Tomographic reconstruction of picosecond acoustic strain propagation
Tomoda, Motonobu, Matsuda, Osamu, Wright, Oliver B., Voti, Roberto Li
Applied Physics Letters, 90, 4, 041114-1, 3, AMER INST PHYSICS, 2007, [Peer-reviewed]
English, Scientific journal, By means of an ultrafast optical technique, picosecond acoustic strain pulses in a transparent medium are tomographically visualized. The authors reconstruct strain pulses in Au-coated glass from time-domain reflectivity changes as a function of the optical angle of incidence, with similar to 1 ps temporal and similar to 100 nm spatial resolutions. (c) 2007 American Institute of Physics.

A Green's function method for surface acoustic waves in functionally graded materials
Matsuda, Osamu, Glorieux, Christ
Journal of the Acoustical Society of America, 121, 6, 3437, 3445, ACOUSTICAL SOC AMER AMER INST PHYSICS, 2007, [Peer-reviewed]
English, Scientific journal, Acoustic wave propagation in anisotropic media with one-dimensional inhomogeneity is discussed. Using a Green's function approach, the wave equation with inhomogeneous variation of elastic property and mass density is transformed into an integral equation, which is then solved numerically. The method is applied to find the dispersion relation of surface acoustic waves for a medium with continuously or discontinuously varying elastic property and mass density profiles. (c) 2007 Acoustical Society of America.

Microscale multiple scattering of coherent surface acoustic wave packets probed with gigahertz time-reversal acoustics
Tournat, V., Profunser, D. M., Muramoto, E., Matsuda, O., Takezaki, T., Sueoka, S., Wright, O. B.
Physical Review E, 74, 2, 026604-1, 5, AMERICAN PHYSICAL SOC, 2006, [Peer-reviewed]
English, Scientific journal, The multiple scattering of coherent surface acoustic wave packets in a microstructure is studied using an ultrafast optical technique. By recording a set of acoustic transfer functions, we show that it is possible to implement time-reversal acoustics and refocus the wave packets up to the GHz range, two orders of magnitude higher than usual. Many applications in time-reversal acoustics are thus transposable to correspondingly smaller structures, opening the way to efficient nondestructive characterization and manipulation of multiple scattering on the microscale.

Imaging ripples on phononic crystals reveals acoustic band structure and Bloch harmonics
Profunser, Dieter M., Wright, Oliver B., Matsuda, O.
Physical Review Letters, 97, 5, 055502-1, 4, AMER PHYSICAL SOC, 2006, [Peer-reviewed]
English, Scientific journal, Broadband surface phonon wave packets on a phononic crystal made up of a microstructured line pattern are tracked in two dimensions and in real time with an ultrafast optical technique. The eigenmode distribution and the 2D acoustic band structure are obtained from spatiotemporal Fourier transforms of the data up to 1 GHz. We find stop bands at the zone boundaries for both leaky-longitudinal and Rayleigh waves, and show how the structure of individual acoustic eigenmodes in k space depends on Bloch harmonics and on mode coupling.

Time-resolved surface acoustic wave propagation across a single grain boundary
Hurley, DH, Wright, OB, Matsuda, O, Suzuki, T, Tamura, S, Sugawara, Y
Physical Review B, 73, 12, 125403-1, 6, AMERICAN PHYSICAL SOC, 2006, [Peer-reviewed]
English, Scientific journal, Using an optical technique, we present time-resolved measurements of high frequency surface acoustic waves propagating across the boundary between two single crystals. The choice of the elastically anisotropic cubic crystal copper allows the observation of anisotropic surface acoustic propagation with cuspidal wave fronts together with refraction in the presence of significant orientation mismatch. The effect of the subsurface grain boundary angle on the transmitted acoustic field is revealed.

Scanning ultrafast Sagnac interferometry for imaging two-dimensional surface wave propagation
Tachizaki, T, Muroya, T, Matsuda, O, Sugawara, Y, Hurley, DH, Wright, OB
Review of Scientific Instruments, 77, 4, 043713-1, 12, AMER INST PHYSICS, 2006, [Peer-reviewed]
English, Scientific journal, We describe an improved two-dimensional optical scanning technique combined with an ultrafast Sagnac interferometer for delayed-probe imaging of surface wave propagation. We demonstrate the operation of this system, which involves the use of a single focusing objective, by monitoring surface acoustic wave propagation on opaque substrates with picosecond temporal and micron lateral resolutions. An improvement in the lateral resolution by a factor of 3 is achieved in comparison with previous setups for similar samples. (c) 2006 American Institute of Physics.

In situ monitoring of the growth of ice films by laser picosecond acoustics
Kashiwada, Saori, Matsuda, Osamu, Baumberg, Jeremy J., Li Voti, Roberto, Wright, Oliver B.
Journal of Applied Physics, 100, 7, 073506-1, 6, AMER INST PHYSICS, 2006, [Peer-reviewed]
English, Scientific journal, Ultrashort optical pulses are used to excite and probe picosecond acoustic pulses in a sample consisting of an opaque material upon which ice is continuously deposited from the vapor phase at similar to 110 K. By analysis of the ultrasonic propagation and reflection inside the submicron ice film and taking into account the scattering of the probe light by the acoustic waves, the thickness, sound velocity, refractive index, ultrasonic attenuation, and photoelastic constant of the ice film are derived. This method should find applications for the in situ monitoring of thin transparent films during growth. (c) 2006 American Institute of Physics.

High frequency surface waves scattered in microstructured phononic crystals
Dieter M. Profunser, Oliver B. Wright, Osamu Matsuda, Udo Lang, Khelif Abdelkrim, Sarah Benchabane, Vincent Laude
2006 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-5, PROCEEDINGS, 501, +, IEEE, 2006, [Peer-reviewed]
English, International conference proceedings, Using an ultrafast optical technique, broadband surface acoustic wave packets are tracked on 1D and 2D phononic crystals in two dimensions in real time at frequencies up to similar to 1 GHz. The acoustic band structure is obtained from the data by means of a spatiotemporal Fourier transform. We find stop bands for both leaky longitudinal and Rayleigh waves.

Erratum: "Real time imaging of surface acoustic waves on crystals and microstructures" (Japanese Journal of Applied Physics (2005) 44 (4292))
Oliver B. Wright, Osamu Matsuda, Yoshihiro Sugawara
Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 44, 10, 7733, 11 Oct. 2005, [Peer-reviewed]
English, Scientific journal

Acoustic phonon generation and detection in GaAs/Al 0.3Ga 0.7As quantum wells with picosecond laser pulses
O. Matsuda, T. Tachizaki, T. Fukui, J. J. Baumberg, O. B. Wright
Physical Review B - Condensed Matter and Materials Physics, 71, 11, 15 Mar. 2005, [Peer-reviewed]
English, Scientific journal, Picosecond acoustic-phonon pulse generation and detection is investigated in a sample containing three GaAs/Al 0.3Ga 0.7As quantum wells of different thickness with an interferometric optical pump and probe technique. The pump photon energy is tuned through the hh1-e1 transitions of each well and the probe photon energy is chosen to allow the detection of the phonon pulses at the sample surface. The phonon pulse shapes are explained with a model that relates the carrier wave functions to the acoustic strain, and the acoustic strain to the detected optical reflectance and phase changes. ©2005 The American Physical Society.

Direct measurement of ultrafast surface displacement in laser picosecond acoustics
Matsuda, O, Aoki, K, Tachizaki, T, Wright, OB
Journal De Physique Iv, 125, 361, 363, E D P SCIENCES, 2005, [Peer-reviewed]
English, Scientific journal, Picosecond acoustic pulses generated in solids with ultrashort optical pulses can be detected through the reflectance or phase changes of optical probe pulses. The detection relies on acousto-optic coupling resulting from a combination of the photoelastic effect and transient surface displacements. The acoustic strain pulse shape gives access to the ultrafast dynamics of the electrons that influence the generation process. This pulse shape is directly related to the contribution to the probe light modulation resulting from surface displacement. Here we present a method that allows the discrimination between the photoelastic and surface displacement contributions using a novel oblique optical incidence geometry, allowing the strain pulse shape to be directly obtained in a single measurement.

Acoustic phonon generation and detection in GaAs/Al0.3Ga0.7As quantum wells with picosecond laser pulses
Matsuda, O, Tachizaki, T, Fukui, T, Baumberg, JJ, Wright, OB
Physical Review B, 71, 11, 115330-1, 13, AMER PHYSICAL SOC, 2005, [Peer-reviewed]
English, Scientific journal, Picosecond acoustic-phonon pulse generation and detection is investigated in a sample containing three GaAs/Al0.3Ga0.7As quantum wells of different thickness with an interferometric optical pump and probe technique. The pump photon energy is tuned through the hh1-e1 transitions of each well and the probe photon energy is chosen to allow the detection of the phonon pulses at the sample surface. The phonon pulse shapes are explained with a model that relates the carrier wave functions to the acoustic strain, and the acoustic strain to the detected optical reflectance and phase changes.

Real time imaging of surface acoustic waves on crystals and microstructures
Wright, OB, Matsuda, O, Sugawara, Y
Japanese Journal of Applied Physics Part 1-Regular Papers Brief Communications & Review Papers, 44, 6B, 4292, 4296, JAPAN SOC APPLIED PHYSICS, 2005, [Peer-reviewed]
English, Scientific journal

Terahertz ultrasonic generation and detection in GaAs/AlGaAs quantum wells
Tachizaki, T, Matsuda, O, Fukui, T, Baumberg, JJ, Wright, OB
Japanese Journal of Applied Physics Part 1-Regular Papers Brief Communications & Review Papers, 44, 6B, 4477, 4479, JAPAN SOC APPLIED PHYSICS, 2005, [Peer-reviewed]
English, Scientific journal, High frequency ultrasonic pulse generation and detection are investigated in a sample with three embedded GaAs/Al(0.3)Ga(0.7)As quantum wells by means of ultrashort optical pulses. The experimental results, showing that ultrasonic frequencies up to 0.5THz are detected, are compared with numerical simulations of the ultrasonic pulse generation, propagation and attenuation, and of the optical detection process. The effective optical extinction coefficients of the embedded quantum wells and the ultrasonic attenuation coefficient of Al(0.3)Ga(0.7)As are determined from the analysis.

Ultrafast Spectroscopy Using Ultrashort Acoustic Pulses Generated and Detected by Picosecond Light Pulses
MATSUDA Osamu, WRIGHT Oliver B
Japanese journal of optics, 34, 2, 69, 74, 応用物理学会分科会日本光学会, 2005, [Peer-reviewed]
Japanese, Scientific journal

Real time imaging of surface acoustic waves on crystals and microstructures (vol 44, pg 4292, 2005)
Wright, OB, Matsuda, O, Sugawara, Y
Japanese Journal of Applied Physics Part 1-Regular Papers Brief Communications & Review Papers, 44, 10, 7733, 7733, JAPAN SOC APPLIED PHYSICS, 2005, [Peer-reviewed]
English, Scientific journal, The use of acoustic pulses to image materials is well-known in echography or sonar applications. We are extending this field by generating point-excited sound pulses on solid surfaces with ultrashort laser pulses and imaging the resulting surface wave propagation in real time. To see the tiny vibrations of the surface, smaller in amplitude than the dimensions of a single atom, we use another set of laser pulses for scanned probing. The typical surface phonon wavelength is of the order of a few microns, corresponding to frequencies up to 1 GHz. With such a system we can watch coherent acoustic wave packets in two dimensions rippling across crystal surfaces and microscopic landscapes.

Real-time imaging of surface acoustic waves : Watching ripples on the microscale
WRIGHT Oliver B, SUGAWARA Yoshihiro, MATSUDA Osamu
應用物理, 73, 6, 732, 740, 応用物理学会, Jun. 2004
Japanese

Laser picosecond acoustics in a two-layer structure with oblique probe light incidence
Matsuda, O, Wright, OB
Ultrasonics, 42, 1-9, 653, 656, ELSEVIER SCIENCE BV, 2004, [Peer-reviewed]
English, Scientific journal, A theory for the analysis of experiments involving laser picosecond acoustics with obliquely incident probe light in a two-layer structure is outlined. The reflectance and phase changes of the reflected light are calculated with a theory that takes into account the effects of multiple optical reflections. The sample consists of a single partially transparent layer on a substrate, both with arbitrary optical constants. We discuss the conditions in which one may discriminate between components of the optical modulation of a probe beam arising from the photoelastic effect and from the displacement of the sample interfaces induced by the acoustic strain. (C) 2004 Elsevier B.V. All rights reserved.

Acoustic phonon pulse generation and detection in GaAs/Al0.3Ga0.7 as quantum wells
T Tachizaki, O Matsuda, T Fukui, JJ Baumberg, OB Wright
PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL. 1, NO. 11, 1, 11, 2749, 2752, WILEY-V C H VERLAG GMBH, 2004, [Peer-reviewed]
English, International conference proceedings, Acoustic phonon pulse generation and detection are investigated in a sample with three embedded GaAs/AlGaAs quantum wells by an ultrafast optical pump and probe technique at the temperatures 20 K and 300 K. Scanning the pump photon energies around the hh1-e1 resonances we find a strong variation of the transient reflectance and phase changes. These changes are compared with a numerical simulation based on probe light scattering due to the inhomogeneous photoelastic effect. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Imaging of surface phonons on a sphere
H Yamazaki, O Matsuda, OB Wright, G Amulele
PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL. 1, NO. 11, 1, 11, 2979, 2982, WILEY-V C H VERLAG GMBH, 2004, [Peer-reviewed]
English, International conference proceedings, Surface phonon wavepackets are generated on aluminium-coated transparent glass balls on irradiation with ultrashort light pulses. Delayed ultrashort probe light pulses are used to image the surface phonon propagation in real time by simply monitoring the modulation in the reflected probe beam intensity caused by the photoelastic effect. Imaging was achieved in the region of the phonon source and at the opposite pole of the sphere. (C) 2004 WILEY-VCH Verlag GmbH & Co. MaA, Weinheim.

Nanosecond and picosecond time reversal acoustics
Tournat, V, OB Wright, O Matsuda
PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL. 1, NO. 11, 1, 11, 2737, 2740, WILEY-V C H VERLAG GMBH, 2004, [Peer-reviewed]
English, International conference proceedings, We describe a means to achieve time reversal acoustics on nanosecond or picosecond time scales for surface or bulk longitudinal phonon modes, respectively, by the use of ultrashort optical pulses for the phonon generation. After the presentation of the theory of low and high frequency time reversal acoustics, the limitations of the method and possible experiments on nanostructures and microstructures are discussed. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface phonon imaging through the photoelastic effect
H Yamazaki, O Matsuda, OB Wright
PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL. 1, NO. 11, 1, 11, 2991, 2994, WILEY-V C H VERLAG GMBH, 2004, [Peer-reviewed]
English, International conference proceedings, Surface phonon imaging is very useful for testing thin structures, in particular because it allows film thicknesses or elastic constants to be derived. We present a method for imaging surface phonons based on optical reflectivity measurements combined with excitation using picosecond optical pulses. Surface phonons are generated in a thin aluminium. film on a transparent glass substrate. The induced strain modulates the refractive index of the film and substrate through the photoelastic effect. Probe laser pulses incident from the film or substrate side can be used to image surface phonon propagation in real time by simply monitoring the modulation in the reflected probe beam intensity. When we image from the substrate side, surface-skimming longitudinal bulk phonons are clearly imaged in addition to the surface phonons. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coherent shear phonon generation and detection with ultrashort optical pulses
Matsuda, O, Wright, OB, Hurley, DH, Gusev, VE, Shimizu, K
Physical Review Letters, 93, 9, 095501-1, 4, AMER PHYSICAL SOC, 2004, [Peer-reviewed]
English, Scientific journal, Using an optical technique we generate and detect picosecond shear and quasishear coherent acoustic phonon pulses in the time domain. Thermoelastic and piezoelectric generation are directly achieved by breaking the sample lateral symmetry using crystalline anisotropy. We demonstrate efficient detection in isotropic and anisotropic media with various optical incidence geometries.

Acoustic phonon pulse generation and detection in GaAs/Al 0.3Ga0.7As quantum wells
Takehiro Tachizaki, Osamu Matsuda, Takashi Fukui, Jeremy J. Baumberg, Oliver B. Wright
Physica Status Solidi C: Conferences, 1, 11, 2749, 2752, 2004, [Peer-reviewed]
English, International conference proceedings, Acoustic phonon pulse generation and detection are investigated in a sample with three embedded GaAs/AlGaAs quantum wells by an ultrafast optical pump and probe technique at the temperatures 20 K and 300 K. Scanning the pump photon energies around the hh1-e1 resonances we find a strong variation of the transient reflectance and phase changes. These changes are compared with a numerical simulation based on probe light scattering due to the inhomogeneous photoelastic effect. © 2004 WILEY-VCH Verlag GmbH &
Co. KGaA, Weinheim.

Surface phonon imaging through the photoelastic effect
Hiroto Yamazaki, Osamu Matsuda, Oliver B. Wright
Physica Status Solidi C: Conferences, 1, 11, 2991, 2994, 2004, [Peer-reviewed]
English, International conference proceedings, Surface phonon imaging is very useful for testing thin structures, in particular because it allows film thicknesses or elastic constants to be derived. We present a method for imaging surface phonons based on optical reflectivity measurements combined with excitation using picosecond optical pulses. Surface phonons are generated in a thin aluminium film on a transparent glass substrate. The induced strain modulates the refractive index of the film and substrate through the photoelastic effect. Probe laser pulses incident from the film or substrate side can be used to image surface phonon propagation in real time by simply monitoring the modulation in the reflected probe beam intensity. When we image from the substrate side, surface-skimming longitudinal bulk phonons are clearly imaged in addition to the surface phonons. © 2004 WILEY-VCH Verlag GmbH &
Co. KGaA. Weinheim.

Nanosecond and picosecond time reversal acoustics
Vincent Tournat, Oliver B. Wright, Osamu Matsuda
Physica Status Solidi C: Conferences, 1, 11, 2737, 2740, 2004, [Peer-reviewed]
English, International conference proceedings, We describe a means to achieve time reversal acoustics on nanosecond or picosecond time scales for surface or bulk longitudinal phonon modes, respectively, by the use of ultrashort optical pulses for the phonon generation. After the presentation of the theory of low and high frequency time reversal acoustics, the limitations of the method and possible experiments on nanostructures and microstructures are discussed. © 2004 WILEY-VCH Verlag GmbH &
Co. KGaA, Weinheim.

Picosecond acoustic phonon pulse generation in nickel and chromium
T. Saito, O. Matsuda, O. B. Wright
Physical Review B - Condensed Matter and Materials Physics, 67, 20, 28 May 2003, [Peer-reviewed]
English, Scientific journal, The generation mechanisms for picosecond acoustic phonon pulses excited by ultrashort optical pulses in metals with strong electron-phonon coupling are elucidated. By means of an interferometric probing technique to extract changes in optical phase and amplitude, the acoustic pulse shapes in the transition metals Ni and Cr are shown to be governed by both thermal and nonequilibrium electron diffusion. Quantitative comparison of the results with a model that takes into account the nonequilibrium electron dynamics and ultrasonic attenuation gives excellent agreement. © 2003 The American Physical Society.

Direct access to the dispersion relations of multiple anisotropic surface acoustic modes by Fourier image analysis
Sugawara, Y, Wright, OB, Matsuda, O
Applied Physics Letters, 83, 7, 1340, 1342, AMER INST PHYSICS, 2003, [Peer-reviewed]
English, Scientific journal, We present a method based on a combination of temporal and spatial Fourier image analysis, involving the incorporation of a time-reversed acoustic propagation component, that can be used to obtain the angular dispersion or general dispersion relations of multiple surface acoustic modes excited by a localized pulsed source. The method is applied to the study of acoustic propagation at the surface of the highly anisotropic single-crystal TeO2 coated with a thin gold film. (C) 2003 American Institute of Physics.

Laser picosecond acoustics with oblique probe light incidence
Matsuda, O, Wright, OB
Review of Scientific Instruments, 74, 1, 895, 897, AMER INST PHYSICS, 2003, [Peer-reviewed]
English, Scientific journal, Laser picosecond acoustics involves the excitation and detection of picosecond acoustic strain pulses in thin films with ultrashort light pulses. The use of oblique probe light incidence permits a greater degree of freedom in choosing the optical probing conditions and thereby should allow the extraction of more information about the profile of the propagating acoustic strain pulses. Here, we present a theory for the modulation of light reflected at oblique incidence from a solid containing an acoustic strain distribution. The theory can account for the real and imaginary parts of the reflectance variation, and involves both the effect of the transient surface motion and of the photoelastically modulated dielectric constants in the solid. We show, in particular, how the theory can be applied to extract the contribution to the reflectance change arising from the surface motion in an opaque isotropic solid, thereby allowing direct access to the shape of the acoustic strain pulse propagating therein. (C) 2003 American Institute of Physics.

Electron dynamics in chromium probed with 20-fs optical pulses
Hirori, H, Tachizaki, T, Matsuda, O, Wright, OB
Physical Review B, 68, 11, 113102-1, 4, AMER PHYSICAL SOC, 2003, [Peer-reviewed]
English, Scientific journal, Electron excitation and relaxation in chromium are probed with 20-fs time resolution using an ultrafast optical technique. We obtain good fits to the data for the transient reflectivity and transmittivity changes in a thin film using a simple model of electron relaxation, suggesting the existence of an efficient electron-electron thermalization process on ultrashort-time scales. Quantitative analysis allows the extraction of thermo-optic coefficients and dielectric constant variations related to both the electron and the lattice temperatures.

Real-time imaging of surface acoustic waves in thin films and microstructures on opaque substrates (invited)
Sugawara, Y, Wright, OB, Matsuda, O
Review of Scientific Instruments, 74, 1, 519, 522, AMER INST PHYSICS, 2003, [Peer-reviewed]
English, Scientific journal, We present a real-time imaging technique for surface acoustic waves on samples with opaque substrates. We image the surface acoustic wave propagation on a silicon substrate coated with a gold film, and derive the dispersion relation for propagation in symmetry directions. In addition, we image surface acoustic waves at frequencies up to 2 GHz on a diamond substrate coated with a gold film, and on a microstructure deposited on a silicon substrate. (C) 2003 American Institute of Physics.

Picosecond acoustic phonon pulse generation in nickel and chromium
Saito, T, Matsuda, O, Wright, OB
Physical Review B, 67, 20, 205421-1, 7, AMER PHYSICAL SOC, 2003, [Peer-reviewed]
English, Scientific journal, The generation mechanisms for picosecond acoustic phonon pulses excited by ultrashort optical pulses in metals with strong electron-phonon coupling are elucidated. By means of an interferometric probing technique to extract changes in optical phase and amplitude, the acoustic pulse shapes in the transition metals Ni and Cr are shown to be governed by both thermal and nonequilibrium electron diffusion. Quantitative comparison of the results with a model that takes into account the nonequilibrium electron dynamics and ultrasonic attenuation gives excellent agreement.

Electron dynamics in chromium probed with 20-fs optical pulses
H. Hirori, T. Tachizaki, O. Matsuda, O. B. Wright
Physical Review B - Condensed Matter and Materials Physics, 68, 11, 1131021, 1131024, 2003, [Peer-reviewed]
English, Scientific journal, Electron excitation and relaxation in chromium are probed with 20-fs time resolution using an ultrafast optical technique. We obtain good fits to the data for the transient reflectivity and transmittivity changes in a thin film using a simple model of electron relaxation, suggesting the existence of an efficient electron-electron thermalization process on ultrashort-time scales. Quantitative analysis allows the extraction of thermo-optic coefficients and dielectric constant variations related to both the electron and the lattice temperatures.

解説 超音波力顕微鏡のカンチレバーダイナミクス--局所弾性・粘着性の定量的マッピングに向けて
松田 理, 寺田 卓哉, 稲垣 克彦
超音波techno, 15, 1, 51, 54, 日本工業出版, Jan. 2003
Japanese

解説 固体の波紋の観測--弾性表面波の実時間イメージング
菅原 美博, Wright Oliver B, 松田 理
超音波techno, 15, 1, 47, 50, 日本工業出版, Jan. 2003
Japanese

Interferometry: Watching Ripples on Crystals With a Sagnac Interferometer
Yoshihiro Sugawara, Oliver B. Wright, Osamu Matsuda
Optics and Photonics News, 13, 12, 20, Dec. 2002
English, Scientific journal

Wavelength selective photoexcitation of picosecond acoustic-phonon pulses in a triple GaAs/Al0.3Ga0.7As quantum well structure
Matsuda, O, Ishii, I, Fukui, T, Baumberg, JJ, Wright, OB
Physica B-Condensed Matter, 316, 205, 208, ELSEVIER SCIENCE BV, 2002, [Peer-reviewed]
English, Scientific journal, Ultrashort coherent phonon-pulse generation and detection is investigated in a GaAs-Al0.3Ga0.7As quantum well structure containing three wells of different widths using an optical pump and probe method. The pump photon energy is tuned to the region of the hhl-el transition energies of the wells and the probe photon energy is chosen for detection of the phonon pulses that reach the sample surface. By studying the dependence of the probe reflectance change on the pump photon energy, we demonstrate the possibility of wavelength-selective excitation of picosecond acoustic-phonon pulses in quantum wells. (C) 2002 Elsevier Science B.V. All rights reserved.

Spatiotemporal mapping of surface acoustic waves in isotropic and anisotropic materials
Sugawara, Y, Wright, OB, Matsuda, O, Gusev, VE
Ultrasonics, 40, 1-8, 55, 59, ELSEVIER SCIENCE BV, 2002, [Peer-reviewed]
English, Scientific journal, We demonstrate a new method for a real-time imaging of surface acoustic waves at frequencies up to 1 GHz with picosecond temporal and micron spatial resolutions using an ultrafast optical pump and probe technique combined with a common path interferometer. Using samples with isotropic or anisotropic substrates coated with metallic thin films, we observe the propagation of Rayleigh-like modes and surface-skimming bulk modes as well as resolving surface phonon focusing effects. In addition we image surface acoustic wave propagation in a laterally inhomogeneous sample. (C) 2002 Elsevier Science B.V. All rights reserved.

Watching ripples on crystals
Sugawara, Y, Wright, OB, Matsuda, O, Takigahira, M, Tanaka, Y, Tamura, S, Gusev, VE
Physical Review Letters, 88, 18, 185504-1, 4, AMERICAN PHYSICAL SOC, 2002, [Peer-reviewed]
English, Scientific journal, We present a new method for imaging surface phonon focusing and dispersion at frequencies up to 1 GHz that makes use of ultrafast optical excitation and detection. Animations of coherent surface phonon wave packets emanating from a point source on isotropic and anisotropic solids are obtained with micron lateral resolution. We resolve rounded-square shaped wave fronts on the (100) plane of LiF and discover isolated pockets of pseudosurface wave propagation with exceptionally high group velocity in the (001) plane of TeO2 . Surface phonon refraction and concentration in a minute gold pyramid is also revealed.

Real-time imaging and dispersion of surface phonons in isotropic and anisotropic materials
Wright, OB, Sugawara, Y, Matsuda, O, Takigahira, M, Tanaka, Y, Tamura, S, Gesev, VE
Physica B-Condensed Matter, 316, 29, 34, ELSEVIER SCIENCE BV, 2002, [Peer-reviewed]
English, Scientific journal, Surface phonon propagation in anisotropic thin film structures displays beautiful and complex wavefronts. Using an interferometric optical pump and probe technique, we have imaged the propagation of surface phonons at frequencies up to 1 GHz in real time, allowing 'movies' of their wavefronts to be made with picosecond temporal and micron spatial resolutions. We image the propagation on various isotropic and anisotropic thin film structures, and give examples of how the dispersion relation can be directly derived from such movies. (C) 2002 Elsevier Science B.V. All rights reserved.

Laser picosecond acoustics in multilayer structures
Matsuda, O, Wright, OB
Ultrasonics, 40, 1-8, 753, 756, ELSEVIER SCIENCE BV, 2002, [Peer-reviewed]
English, Scientific journal, The field of laser picosecond acoustics has thrived owing to the ease of detection of propagating picosecond acoustic pulses through changes in optical reflectance. Reflectance changes are caused by the inhomogeneous modulation of the refractive index by the propagating elastic strain through the photoelastic effect and also by the associated induced motion of the surface and interfaces. In this paper we present a general formula for calculating the reflectance change based on a rigorous one-dimensional treatment of the perturbation in optical properties of arbitrary multilayer structures, The theory is applied to the quantitative analysis of data obtained by laser picosecond acoustics for a SiO2-Cr double-layer film on a fused silica substrate. The analysis allows the discrimination of the photoelastic contribution and the surface or interface motion contribution to the experimental reflectance variation. (C) 2002 Elsevier Science B.V. All rights reserved.

Cantilever dynamics in ultrasonic force microscopy
Matsuda, O, Terada, T, Inagaki, K, Wright, OB
Japanese Journal of Applied Physics Part 1-Regular Papers Short Notes & Review Papers, 41, 5B, 3545, 3546, INST PURE APPLIED PHYSICS, 2002, [Peer-reviewed]
English, Scientific journal, Ultrasonic force microscopy allows the local mapping of elasticity in atomic force microscopy by the application of ultrasonic vibration to the cantilever or sample. In an attempt to analyse the results of ultrasonic force microscopy in a quantitative fashion, a force-distance curve measurement is done with ultrasonic vibration applied to the cantilever base, and the results are compared with a model of the cantilever dynamics and tip-sample interaction based on the finite-difference technique.

Ultrafast acoustic phonon pulse generation in chromium
Saito, T, Matsuda, O, Wright, OB
Physica B-Condensed Matter, 316, 304, 307, ELSEVIER SCIENCE BV, 2002, [Peer-reviewed]
English, Scientific journal, The generation mechanisms for longitudinal acoustic-phonon pulses excited in the transition metal chromium with sub-picosecond optical pulses are studied. The temporal and spatial evolution of the electron and lattice temperatures up to several picoseconds after laser photon absorption have a major impact on the final profile of the acoustic-phonon pulses. These phonon pulse shapes can be explained by considering both thermal and electron diffusion, and taking into account the effects of frequency-dependent ultrasonic attenuation. (C) 2002 Elsevier Science B.V. All rights reserved.

Reflection and transmission of light in multilayers perturbed by picosecond strain pulse propagation
Matsuda, O, Wright, OB
Journal of the Optical Society of America B-Optical Physics, 19, 12, 3028, 3041, OPTICAL SOC AMER, 2002, [Peer-reviewed]
English, Scientific journal, We derive analytical formulas for the modulation of the reflectance and transmittance of light normally incident on a multilayer thin-film structure whose refractive indices are perturbed by an ultrashort optical pulse. The formulas, expressed in compact form, should prove useful for analysis of a wide range of ultrashort time-scale experiments on multilayers as well as longer time-scale photoacoustic and photothermal experiments based on optical probing. We demonstrate our method by the analysis of the modulated reflectance variation of a SiO2/Cr structure in which picosecond acoustic pulses have been optically excited. (C) 2002 Optical Society of America.

Hysteresis of the cantilever shift in ultrasonic force microscopy
Inagaki, K, Matsuda, O, Wright, OB
Applied Physics Letters, 80, 13, 2386, 2388, AMER INST PHYSICS, 2002, [Peer-reviewed]
English, Scientific journal, We propose a technique based on ultrasonic force microscopy that exploits the hysteresis in cantilever jumping to and from a sample while varying the ultrasonic amplitude. Both the elastic modulus and the work of adhesion can be determined by comparision with a relation derived between their ratio and the cantilever shift at the jump-in point. The method is applied to measurements on an aluminum thin film. (C) 2002 American Institute of Physics.

Photothermal probing of inhomogeneously modulated transparent thin films
Wright, OB, Li Voti, R, Matsuda, O, Larciprete, MC, Sibilia, C, Bertolotti, M
Journal of Applied Physics, 91, 8, 5002, 5009, AMER INST PHYSICS, 2002, [Peer-reviewed]
English, Scientific journal, The problem of the photothermal modulation of optical beams passing through multilayer films is an extremely complex one owing to the inhomogeneously modulated refractive index combined with multiple optical reflections inside the sample. This problem has so far not been given an exact analytical treatment in the field of photothermal probing. We consider here such a treatment for normal-incidence optical probing in reflectance of photothermally modulated single-layer thin-film samples with arbitrary optical constants. The validity of the method is demonstrated by application to a thin transparent film of silica on a silicon substrate. (C) 2002 American Institute of Physics.

Theory of detection of shear strain pulses with laser picosecond acoustics
Matsuda, O, Wright, OB
Analytical Sciences, 17, S216, S218, JAPAN SOC ANALYTICAL CHEMISTRY, 2001, [Peer-reviewed]
English, Scientific journal, The principles of the photo-detection of shear acoustic waves in laser picosecond acoustics are discussed. The shear strain in an isotropic material induces off-diagonal components in the dielectric tensor, that is, the material shows strain induced birefringence. By considering the light reflection from the surface of a birefringent material, it is proved that one needs 1) non-normal incidence of probe light, 2) a shear direction perpendicular to the plane of incidence, and 3) both S and P polarization components of the probe light, for efficient shear strain detection.

Ultrafast carrier diffusion in gallium arsenide probed with picosecond acoustic pulses
Wright, OB, Perrin, B, Matsuda, O, Gusev, VE
Physical Review B, 64, 8, 081202-1, 4, AMER PHYSICAL SOC, 2001, [Peer-reviewed]
English, Scientific journal, We describe an experimental investigation of the generation and detection of picosecond acoustic-phonon pulses in a thin slab of GaAs using ultrashort optical pulses. Comparison of the optical phase variation with a simple theory for ambipolar diffusion indicates that carrier diffusion has a significant effect on the shape of the phonon pulses generated. The phonon pulse duration is measured to be similar to 25 ps, four times longer than that expected from optical-absorption considerations alone, indicating that hot carriers penetrate more than 100 nm into the sample during the phonon pulse generation process.

Ultrafast carrier diffusion in gallium arsenide probed with picosecond acoustic pulses
O. B. Wright, O. Matsuda, B. Perrin, V. E. Gusev
Physical Review B - Condensed Matter and Materials Physics, 64, 8, 2001, [Peer-reviewed]
English, Scientific journal, We describe an experimental investigation of the generation and detection of picosecond acoustic-phonon pulses in a thin slab of GaAs using ultrashort optical pulses. Comparison of the optical phase variation with a simple theory for ambipolar diffusion indicates that carrier diffusion has a significant effect on the shape of the phonon pulses generated. The phonon pulse duration is measured to be ∼25 ps, four times longer than that expected from optical-absorption considerations alone, indicating that hot carriers penetrate more than 100 nm into the sample during the phonon pulse generation process. © 2001 The American Physical Society.

Stiffness transition and connectivity in amorphous chalcogenide semiconductors
Y Wang, T Nakaoka, M Nakamura, O Matsuda, K Murase
PROCEEDINGS OF THE 25TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS, PTS I AND II, 87, 228, 229, SPRINGER-VERLAG BERLIN, 2001, [Peer-reviewed]
English, International conference proceedings, GexSe1-x glasses have been investigated by Raman scattering. The ability of crystallization is obtained by studies of heating glasses from room temperature up to 1000 K. To understand the low-frequency dynamics of the network, we propose a fractal-structure view and a qualitative degree of the fragility. Transition with the connectivity for each studied property is universally related to the stiffness transition, derived from the concept of the constraint theory.

Correlation of structural relaxation at glass transition with network connectivity in GexSe1-x glasses
T Nakaoka, Y Wang, O Matsuda, K Inoue, K Murase
PROCEEDINGS OF THE 25TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS, PTS I AND II, 87, 1687, 1688, SPRINGER-VERLAG BERLIN, 2001, [Peer-reviewed]
English, International conference proceedings, We have investigated the structural relaxations by Raman scattering (10-350 cm(-1)) in GexSe1-x glasses (0.07 less than or equal to x less than or equal to 0.35). Around and above the glass transition temperature, strong quasielastic scattering is observed in the low-frequency spectra (10-90 cm(-1)) of floppy glasses (x less than or equal to 0.20). On the other hand, in rigid glasses (x greater than or equal to 0.23), the strong quasielastic contribution cannot be detected in our spectra. We discuss the transition of the relaxational dynamics from floppy glasses to rigid ones in terms of the constraint counting theory. The distinctness of the transition demonstrates a self-organization of the network.

Femtosecond optical excitation of acoustic phonons in bulk GaAs
OB Wright, B Perrin, O Matsuda, VE Gusev
PROCEEDINGS OF THE 25TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS, PTS I AND II, 87, 192, 193, SPRINGER-VERLAG BERLIN, 2001, [Peer-reviewed]
English, International conference proceedings, Femtosecond spectroscopy of semiconductors has been extensively studied because it provides a window for the observation of ultrafast carrier distributions. Here we report an experimental investigation of the ultrafast coherent acoustic phonon generation mechanisms in bulk GaAs with ultrashort optical pulses. Comparison with a simple theory for ambipolar diffusion indicates that carrier diffusion has a significant effect on the spectrum of the phonon pulses generated.

Generation and detection of picosecond acoustic phonon pulses in a double quantum well structure
Ishii, I, O Matsuda, T Fukui, JJ Baumberg, OB Wright
PROCEEDINGS OF THE 25TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS, PTS I AND II, 87, 871, 872, SPRINGER-VERLAG BERLIN, 2001, [Peer-reviewed]
English, International conference proceedings, Coherent acoustic phonon pulses are excited and detected in a GaAs/Al-0.3 Ga-0.7 As double quantum well structure using femtosecond optical Pulses, The wavelength of the infrared pump light is chosen to selectively generate picosecond acoustic phonon pulses in two buried quantum wells. The wavelength of the probe light pulses is chosen to allow phonon pulse detection in the near-surface region of the sample. Using an interferometric detection technique both reflectivity and phase variations of the probe beam are monitored, an the phonon pulses generated in the well regions are clearly observed in both these variations. An excellent agreement is obtained when the data is compared to a model accounting for the transient surface displacement combined with the spatially distributed variations in refractive index.

Reversible photoinduced structural changes in GeSe2 glass at low-temperature
T Nakaoka, Y Wang, O Matsuda, K Inoue, K Murase
PROCEEDINGS OF THE 25TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS, PTS I AND II, 87, 113, 114, SPRINGER-VERLAG BERLIN, 2001, [Peer-reviewed]
English, International conference proceedings, We have observed resonant Raman enhancement of stretching vibration of Se-Se bonds relative to breathing vibration of GeSe4/2 tetrahedra at room temperature and 15 K in GeSe2 chalcogenide semiconducting glass. At 15 K, structural changes by illumination, which cause photodarkening, induce excess resonant enhancement. After the structural changes are saturated, we can observe a reversible change with the excitation power in resonant Raman spectra. It is found that the origin of the the reversible power dependence is the same as that of the excess resonant enhancement. Both of them are attributed to three-fold coordinated Se atoms forming Se-Se bonds, which cause the photodarkening.

Resonant Raman scattering in crystalline GeSe2
T Nakaoka, Y Wang, K Murase, O Matsuda, K Inoue
PHYSICAL REVIEW B, 61, 23, 15569, 15572, AMER PHYSICAL SOC, Jun. 2000, [Peer-reviewed]
English, Scientific journal, The relationship between the local structures and the electronic stares of layered crystalline GeSe2 are studied by resonant Raman scattering. We observe 34 Raman-active modes of symmetry A(g), and find a selective resonant enhancement of the modes. Almost all the modes are enhanced around 2.7 eV except the two modes. This selective enhancement is attributed to the resonant effect with the localized exciton. We find the essential difference in the atomic motions between the resonant and nonresonant modes. Such behaviors are explained by a structural model of the localized exciton.

Effect of thermal annealing on dynamics of photoluminescence in a-GeSe2 films
Wang, Y, Komamine, T, Nakaoka, T, Matsuda, O, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 266, Pt.B, 904, 907, ELSEVIER SCIENCE BV, 2000, [Peer-reviewed]
English, Scientific journal, We have investigated the effect of thermal annealing on dynamics of photoluminescence (PL) in vacuum-evaporated a-GeSe2 films with thickness of 15 mu m. The intensity of PL increases over 200 times after annealing at 250 degrees C, which makes it possible to take a first investigation on both decay time and fatigue effect. The disordered amorphous structure of the a-GeSe2 film, containing wrong bonds, Ge-Ge and Se-Se, has been reconstructed to a stable structure by diminishing the number of the wrong bonds and the related strain or internal pressure by thermal annealing. (C) 2000 Elsevier Science B.V. All rights reserved.

Relaxation process of band-edge exciton in layered crystalline GeSe2
Nakaoka, T, Wang, Y, Matsuda, O, Inoue, K, Murase, K
Journal of Luminescence, 87-9, 617, 619, ELSEVIER SCIENCE BV, 2000, [Peer-reviewed]
English, Scientific journal, Relaxation processes of the photoexcited states in layered crystalline GeSe2 are studied by time-resolved photoluminescence measurement. Two photoluminescence bands, P1 and P2, are clearly resolved from their decay kinetics. It is found that one of the relaxation pathways to the P2 band arises from a band-edge exciton state. The P2 band shows no polarization dependence, in spite of the fact that the photoexcitation of the exciton shows a strongly anisotropic optical character, We discuss the relaxation process on the basis of the luminescence characteristics and the structural model of the band-edge exciton quasi-localized at edge-sharing tetrahedra, (C) 2000 Elsevier Science B.V. All rights reserved.

Temperature dependence of photoluminescence intensity and decay in GeSe2 glass
Matsuda, O, Yamagata, K, Saitoh, Y, Wang, Y, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 266, Pt.B, 908, 912, ELSEVIER SCIENCE BV, 2000, [Peer-reviewed]
English, Scientific journal, The intensity and decay profile of the photoluminescence (PL) in grassy GeSe2 are measured as a function of temperature from 7 to 200 K. The intensity decreases exponentially in the temperature region >100 K. The complicated temperature dependence of the decay profile as well as the dependence of the intensity are explained in a unified framework by adopting a model of the luminescent sites whose thermal activation energy for the non-radiative process is distributed. We show that the intensity variation is affected by the non-radiative process while the decay life time depends almost only on the radiative transition rate. (C) 2000 Elsevier Science B.V. All rights reserved.

Raman-spectroscopy studies on rigidity percolation and fragility in Ge-(S,Se) glasses
Wang, Y, Nakamura, M, Matsuda, O, Murase, K
Journal of Non-Crystalline Solids, 266, Pt.B, 872, 875, ELSEVIER SCIENCE BV, 2000, [Peer-reviewed]
English, Scientific journal, We have investigated the Raman spectra in a range 3-100 cm(-1) in chalcogenide glasses, GexS1-x and GexSe1-x, with 0 less than or equal to x less than or equal to 0.42 in the average coordination number, [r], from 2 to 2.84. The relation between the rigidity percolation, based on the prediction of the mean-held constraint theory, and a relative degree of fragility, representing the structural relaxation of the network, are demonstrated by varying the structures of the glasses. The obtained fragility of the glasses for x < 0.20 ([r] < 2.4) is larger than that for x > 0.20. A decrease of the fragility at about [r] = 2.4 is attributed to the predicted rigidity percolation threshold where the glass changes from floppy to rigid, and mesoscopic structural changes beyond the mean-field theory. For [r] > 2.4, fragility depends on chemical bonds between Ge-Se and Ge-S systems, since the local structure directly contributes to the properties of the overcoordinated network. (C) 2000 Elsevier Science B.V. All rights reserved.

Laser picosecond acoustics in isotropic and anisotropic materials
Hurley, DH, Wright, OB, Matsuda, O, Gusev, VE, Kolosov, OV
Ultrasonics, 38, 1-8, 470, 474, ELSEVIER SCIENCE BV, 2000, [Peer-reviewed]
English, Scientific journal, We present experimental results concerning the laser generation of picosecond acoustic pulses and their propagation in isotropic and anisotropic materials. We make use of a conventional reflectance detection technique as well as interferometric detection to probe the real and imaginary changes in reflectance. We also demonstrate the detection of transverse acoustic waves by mode conversion at an interface between an isotropic polycrystalline film and an anisotropic substrate, (C) 2000 Elsevier Science B.V. All rights reserved.

Resonant Raman scattering in crystalline GeSe2
Nakaoka, T, Wang, Y, Murase, K, Matsuda, O, Inoue, K
Physical Review B, 61, 23, 15569, 15572, 2000, [Peer-reviewed]
English, Scientific journal

Raman scattering investigation of the structure of amorphous silicon in a-Si/SiO2 superlattice films
Wang, Y, Matsuda, O, Serikawa, T, Murase, K
Journal De Physique Iv, 10, P7, 259, 262, E D P SCIENCES, 2000, [Peer-reviewed]
English, Scientific journal, To clarify the structure of amorphous silicon (a-Si), with the thickness less than 5nm, affected by the interface between a-Si and a-SiO2 as well as the structural changes after an annealing of 900 degrees C in N-2 gas atmosphere, Raman scattering investigation is carried out in a-Si/SiO2 superlattice (SL) films prepared by the sputtering method. Vibrational motion of strained a-Si at and near a-Si/SiO2 interface is influenced by the vibration of pressed a-SiO2 at the other side of the interface that results a blue shift of transverse optic (TO) -like modes in a-Si. The narrow space of thin (<2.5 nm in this work) a-Si layer impedes the crystallization to a-Si and the relaxation of energy during the crystallization event.

A study of network dimensionality in chalcogenide glass by low frequency Raman scattering
Nakamura, M, Matsuda, O, Wang, Y, Murase, K
Physica B, 263, 330, 332, ELSEVIER SCIENCE BV, 1999, [Peer-reviewed]
English, Scientific journal, We have measured low frequency Raman spectra in Ge chalcogenide glasses. The dependence of spectral dimensionality of stretching fracton, (d) over tilde(s), on the sample composition is obtained from low frequency reduced Raman spectrum and is correctly correlated to the actual network dimensionality of Ge chalcogenide glasses. The value of (d) over tilde(s) is supposed to be a parameter representing the degree of localization of lattice vibrations and an indicator of network dimensionality of network glasses. The findings on the interpretation of (d) over tilde(s) should be applied in future research of disordered systems. (C) 1999 Elsevier Science B.V. All rights reserved.

Rigidity percolation and structure of Ge-Se system
Wang, Y, Nakamura, M, Matsuda, O, Murase, K
Physica B, 263, 313, 316, ELSEVIER SCIENCE BV, 1999, [Peer-reviewed]
English, Scientific journal, We have investigated low-frequency Raman spectra of glassy GexSe1-x (x = 0-0.40) in a range of 3-100 cm(-1) A relative degree of fragility was first obtained in the Ge-Se system by an investigation of the line shape of low-frequency Raman spectra. The results imply an important relationship between the changes of fragility and the structural changes. The rapid drop of the fragility at average coordination number, [r], of 2.4 (x = 2.0) is considered as evidence for the rigidity threshold predicted by the mean-field constraint counting procedures. (C) 1999 Elsevier Science B.V. All rights reserved.

Temperature dependence of photoluminescence in Mn-doped ZnS retrieved after the pressure-induced structural phase transition
Hanzawa, H, Kobayashi, M, Matsuda, O, Murase, K, Giriat, W
Physica Status Solidi a-Applied Research, 175, 2, 715, 724, WILEY-V C H VERLAG GMBH, 1999, [Peer-reviewed]
English, Scientific journal, The temperature dependence of photoluminescence spectra in Mn-doped ZnS retrieved after the pressure-induced structural phase transition has been studied in the energy range from 0.8 to 2.5 eV. At room temperature, strong photoluminescence with the peak energy of 1.3 eV has been observed, This luminescence band is similar to the near infrared emission band observed in virgin bulk crystals with relatively large Mn concentration. However, the luminescence intensity is much stronger than that in the bulk crystals. The temperature dependence has revealed that the large quantum efficiency at room temperature resulted from the suppression of thermal quenching. At low temperature, the yellow band at 2.1 eV which is caused by the internal transition within the Mn2+ ions and the emission band at 1.6 eV are also observed in the pressure-retrieved samples. In the bulk crystal, a new emission band has been observed near 0.9 eV. The effective phonon energy and the Huang-Rhys factor of these spectra are determined using a configuration coordinate model.

Relation of structural and elastic crossover length investigated by low-frequency Raman scattering in GexSe1-x glasses
Nakamura, M, Matsuda, O, Murase, K
Physical Review B, 57, 17, 10228, 10231, May 1998, [Peer-reviewed]
English, Scientific journal

A Raman scattering investigation of the structure of glassy and liquid Ge(x)Se(1-x)
Wang, Y, Matsuda, O, Inoue, K, Yamamuro, O, Matsuo, T, Murase, K
Journal of Non-Crystalline Solids, 232, 702, 707, ELSEVIER SCIENCE BV, 1998, [Peer-reviewed]
English, Scientific journal, The structures of glassy and liquid GexSe1-x (0.00 less than or equal to x less than or equal to 0.33) and the structural changes occurring at the glass-transition have been investigated, using Raman scattering combined with differential scanning calorimetry. The medium range structures in the glassy and liquid states are discussed in relation to anomalous changes in the Raman spectra at the glass-transition. The characteristic spectrum of crystalline GeSe2 appears, superimposed on that for liquid GexSe1-x, in the composition range 0.18 less than or equal to x less than or equal to 0.33. It is found that the rate of recrystallization shows an abrupt change when x increases from 0.15 to 0.18? although the structure does not change significantly. These results are considered as evidence for a rigidity threshold at an average coordination, [r], of 2.4 (x = 0.20), which is predicted based on mean-field constraint counting procedures. (C) 1998 Elsevier Science B.V. All rights reserved.

Relaxation process of photo-excited states in CeSe(2) glass investigated by time-resolved photoluminescence
Matsuda, O, Saitoh, Y, Yamagata, K, Wada, Y, Wang, Y, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 227, Pt.B, 829, 832, ELSEVIER SCIENCE BV, 1998, [Peer-reviewed]
English, Scientific journal, Time-resolved photoluminescence measurement is done on glassy GeSe2. The decay curve consists of a process whose decay time is about similar to 0.3 ms and a faster process whose decay time is less than 1 mu s. The decay time of the slower process becomes short with increasing excitation energy. The ratio between the slower process and the faster process increases with increasing excitation energy especially in the higher emission energy region. The relaxation process from the excited state just after the photon absorption to the trapped excited state is discussed. (C) 1998 Elsevier Science B.V. AII rights reserved.

Photo-induced crystallization in amorphous GeSe(2) studied by Raman scattering
Wang, Y, Matsuda, O, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 227, Pt.B, 728, 731, ELSEVIER SCIENCE BV, 1998, [Peer-reviewed]
English, Scientific journal, The structural difference, due to different preparation methods, in glassy GeSe2 samples is investigated by photo-induced crystallization phenomena using time-resolved Raman measurement. Crystallization temperatures of two samples, which were cooled from melts at different cooling rates, were almost the same in thermal crystallization processes. However, in photo-induced crystallization processes, threshold temperatures of the crystallization directly depended on their cooling rates, the smaller cooling rate the lower the threshold temperature. In the sample cooled at a smaller cooling rate, its medium-range structure is more similar to crystalline nuclei, or easier to transform into crystalline nuclei. (C) 1998 Elsevier Science B.V. All rights reserved.

Structural changes during photo-induced and thermal crystallization processes in evaporated amorphous GeSe(2) films by Raman scattering
Matsuda, O, Takeuchi, H, Wang, Y, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 232, 554, 559, ELSEVIER SCIENCE BV, 1998, [Peer-reviewed]
English, Scientific journal, The photo-induced and thermal crystallization processes of amorphous GeSe2 films are studied and compared by observation of Raman scattering spectra, Reversible changes of medium range structure are observed in a temperature region well below the crystallization temperature in the thermal crystallization process. This structure is assumed to be caused by large structural fluctuations in the evaporated films. On the other hand, in the photo-induced crystallization process, structural changes are not observed before crystallization begins. The observation is consistent with the fact that the high temperature phase crystal grows much more favorably than the low temperature phase crystal does in the photo-induced crystallization process, though the crystallization temperature is well below the thermal crystallization temperature in the dark. (C) 1995 Elsevier Science B.V. All rights reserved.

Reversible mesoscopic structural transformations in vacuum evaporated amorphous Ge30Se70 film studied by Raman scattering
Takeuchi, H, Matsuda, O, Murase, K
Journal of Non-Crystalline Solids, 238, 1-2, 91, 97, ELSEVIER SCIENCE BV, 1998, [Peer-reviewed]
English, Scientific journal, The Raman scattering properties at high temperatures in non-crystalline Ge30Se70 prepared by melt-quenching (MQ) and vacuum evaporation (VE) are investigated from the view point of the structural difference between them. In the VE film with increasing temperatures, the mesoscopic structure containing edge-sharing GeSe4/2 tetrahedra changes to the structure only containing the corner-sharing tetrahedra even at temperatures well below the glass transition temperature. In the MQ-glass, the structure containing edge-sharing tetrahedra is more stable than that in the VE-film. (C) 1998 Elsevier Science B.V. All rights reserved.

Relation of structural and elastic crossover length investigated by low-frequency Raman scattering in GexSe1-x glasses
Nakamura, M, Matsuda, O, Murase, K
Physical Review B, 57, 17, 10228, 10231, 1998, [Peer-reviewed]
Scientific journal, Low-frequency Raman spectra (10 (Formula presented)-80 (Formula presented) have been studied in the (Formula presented) glasses. The Raman spectra reduced by the Bose factor (Formula presented), which are proportional to the vibrational density of states, show a power-law dependence of the frequency, (Formula presented), (Formula presented) in a low-frequency region. The value (Formula presented) is a noninteger, which suggests that these glassy systems have fractal structures. The spectra (Formula presented) of Se-rich samples are classified into three regions whose vibrational properties are due to acoustic phonons, bending fractons, and stretching fractons, whereas that of the Ge-rich samples’ two regions are due to acoustic phonons and stretching fractons. The difference of two types of these low-frequency properties are explained by correlation of the structural crossover length (Formula presented) and the elastic crossover length (Formula presented) The threshold of these phenomena occurs near (Formula presented), which may be related to the prediction of the Phillips-Thorpe constraint theory. © 1998 The American Physical Society.

Direct deposition of silicon and silicon-oxide films using low-energy Si focused ion beams
Yanagisawa, J, Nakayama, H, Matsuda, O, Murase, K, Gamo, K
Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 127, 893, 896, ELSEVIER SCIENCE BV, 1997, [Peer-reviewed]
English, Scientific journal, Ion beam deposition using low-energy (100 eV) Si2+ focused ion beams (FIB) was performed on gold evaporated substrate at room temperature under various deposition conditions, such as beam scan rates of the FIB and background oxygen pressures of the sample chamber during the deposition. From Auger electron spectroscopy (AES) measurement, it was found that the amount of the oxygen incorporated inside the film can be controlled by the deposition ambient. From the chemical shift in AES spectra and Raman spectroscopy, it was found that deposited Si without oxygen ambient was amorphous and the observed oxygen in the film deposited in high oxygen ambient was chemically bonded with silicon and formed silicon-oxygen bonds,

Structural changes at glass-transition in GexSe1-x studied by Raman scattering
Wang, Y, Matsuda, O, Inoue, K, Murase, K
Progress of Theoretical Physics Supplement, 126, 126, 191, 194, PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE, 1997, [Peer-reviewed]
English, Scientific journal, The glass-transition, crystallization and melting in GexSe1-x (0 less than or equal to x less than or equal to 0.33) have been studied by Raman scattering. Raman spectra exhibit some anomalous changes at the glass-transition. On the basis of these anomalous features which relate to the structural changes, we investigate a medium range structure in glassy and liquid GexSe1-x. In the Ge composition range of 0.04 < x < 0.18, both GeSe2 and Se crystals are much more difficult to be obtained than in the other Ge composition.

Temperature dependence of Raman spectra in amorphous, crystalline and liquid GeSe2
Wang, Y, Nakamura, M, Matsuda, O, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 198, Pt 2, 753, 757, ELSEVIER SCIENCE BV, 1996, [Peer-reviewed]
English, Scientific journal, We have investigated the dynamical processes of glass transition, crystallization and melting in GeSe2 by analyzing Raman spectra of glassy, crystalline and liquid GeSe2 as a function of temperature in a range between room temperature and 730 degrees C. Raman vibration bands related to short- and medium-range structures are observed in glassy and liquid forms. The result suggests that there is a topologically crystalline layer-like fragments in these two forms. The change of the spectral shape around the glass-transition temperature is explained by the decrease of interlayer interaction between the neighboring layer-like fragments consistent with the decrease of the viscosity.

Photoemission and inverse-photoemission study of the electronic structure of p- and n-type amorphous Ge-Se-Bi films
Matsuda, O, Ohba, T, Murase, K, Ono, I, Grekos, P, Kouchi, T, Nakatake, M, Tamura, M, Namatame, H, Hosokawa, S, Taniguchi, M
Journal of Non-Crystalline Solids, 198, Pt 2, 688, 691, ELSEVIER SCIENCE BV, 1996, [Peer-reviewed]
English, Scientific journal, The density of states in the conduction band as well as that in the valence band in amorphous Ge20Si80-xBix and Bi2Se3 thin films has been investigated by inverse-photoemission and ultraviolet photoemission spectroscopies. We have found that, with increasing Bi content, the conduction band minimum approaches the Fermi level, while the valence band maximum remains unchanged with respect to the Fermi level, It is concluded that the mixture of Ge-Se and Bi-Se anti-bonding orbits compose the conduction band of the Ge-Se-Bi system. The origin of the n-type conduction in the high Bi concentration region of Ge20Se80-xBix is attributed to this conduction band which appears just above the Fermi level.

Photoluminescence study of glassy Ge(SxSe1-x)(2)
Wada, Y, Wang, Y, Matsuda, O, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 198, Pt 2, 732, 735, ELSEVIER SCIENCE BV, 1996, [Peer-reviewed]
English, Scientific journal, Photoluminescence spectra of Ge(SxSe1-x), glasses are investigated with respect to their composition and excitation-energy dependence. Even if the S content, x, is increased to 0.99, the photoluminescence spectra mainly involve those of g-GeSe2 glasses as their ingredient. This result indicates that the luminescence mainly occurs in Se-related luminescent centers. The excitation-energy dependence of the photoluminescence intensity of Se-rich and S-rich samples shows a similar tendency to those of GeSe2 and GeS2 glasses, respectively. We conclude that the energy transfer from S sites excited by light to Se sites is responsible for the observed phenomena.

Laser spot size dependence of photo-induced crystallization process in amorphous GeSe2 film
Nakamura, M, Wang, Y, Matsuda, O, Inoue, K, Murase, K
Journal of Non-Crystalline Solids, 198, Pt 2, 740, 743, ELSEVIER SCIENCE BV, 1996, [Peer-reviewed]
English, Scientific journal, The photo-induced crystallization phenomena in amorphous GeSe2 film are studied by time resolved Raman spectroscopy with varying the spot size of the excitation laser light. The enlargement of the spot size increases the growth probability of the low temperature crystalline phase, while the high temperature crystalline phase dominates under the small spot. A model for understanding these results is proposed in terms of the temperature profile under the irradiation area. The fact that the threshold excitation power density at the onset of crystallization is independent of the spot size suggests that the electronic excitation by light plays an important role in the photo-induced crystallization process.

A model calculation of the characteristic Raman modes in the tetrahedral network structures of GeSe2
Inoue, K, Matsuda, O, Murase, K
Physica B-Condensed Matter, 219-20, 520, 522, ELSEVIER SCIENCE BV, 1996, [Peer-reviewed]
English, Scientific journal, The characteristic peaks, A at 211 and A* at 216 cm(-1), in the Raman spectra of layered crystalline GeSe2 have been studied by a model calculation using a valence force field and bond polarizability (VFF-BP). The A phonon is extended along the GeSe4 tetrahedral chain, while the A* phonon is quasi-localized at the edge-sharing GeSe4 tetrahedra. An extended VFF-BP model including interlayer interactions between Se atoms is proposed to understand the peculiar weakness of the A* Raman intensity.

COMPOSITION MODULATION IN QUANTUM-WIRE STRUCTURES ON VICINAL (110)GAAS STUDIED BY PHOTOLUMINESCENCE
INOUE, K, HUANG, HK, TAKEUCHI, M, KIMURA, K, NAKASHIMA, H, IWANE, M, MATSUDA, O, MURASE, K
Japanese Journal of Applied Physics Part 1-Regular Papers Short Notes & Review Papers, 34, 2B, 1342, 1344, 1995, [Peer-reviewed]
English, Scientific journal, Quantum wires are fabricated by the growth of the AlGaAs system on vicinal (110) GaAs substrates misoriented toward (111)A. It is concluded that during the growth of AlGaAs, composition modulation occurs on the large-step structure almost independently of the temperature, while the large-step structure is formed by the growthonly below a transition temperature. The photoluminescence (PL) from a single quantum wire is observed witha much narrower spectral width as compared with the PL from multi-quantum wires. © 1995 The Japan Society of Applied Physics.

ELECTRONIC AND THERMAL-PROCESSES DURING THE PHOTOINDUCED CRYSTALLIZATION OF AMORPHOUS GESE2
MATSUDA, O, OE, H, INOUE, K, MURASE, K
Journal of Non-Crystalline Solids, 193, 524, 528, ELSEVIER SCIENCE BV, 1995, [Peer-reviewed]
English, Scientific journal, The photo-induced crystallization process in amorphous GeSe2. is investigated by time-resolved Raman spectroscopy with continuous or periodic light (4880 Angstrom) from an Ar ion laser. It is shown that the electronic and thermal processes work cooperatively to achieve the photo-crystallization. It is found that the periodic excitation experiments reveal the dynamical aspects of the process during latent periods before the crystallization. In particular, a relatively long dark period (10 ms) in the periodic excitation reverses the evolution process in the amorphous state.

AN INVERSE-PHOTO-EMISSION STUDY ON THE PHOTO-DISSOLUTION OF AG AND CU METALS IN AMORPHOUS GESE2
HOSOKAWA, S, HARI, Y, ONO, I, NISHIHARA, K, TANIGUCHI, M, MATSUDA, O, MURASE, K
Journal of Physics-Condensed Matter, 6, 15, L207, L214, IOP PUBLISHING LTD, 1994, [Peer-reviewed]
English, Scientific journal, The conduction-band density of states of amorphous (a-) GeSe2 photo-dissolved by Ag and Cu metals has been examined by means of inverse-photo-emission spectroscopy (IPES). The characteristic feature of the IPES spectrum of a-GeSe2 rapidly smears out with the photo-dissolution of Ag or Cu metal, and each spectrum of the fully photo-doped samples is quite similar to that of a-GeSe1.5. This result is consistent with a structural model in which the dopant atoms are surrounded by four Se atoms and many Ge-Ge bonds are induced by photo-dissolution. We also measured the change of the IPES spectra in the process of Ag photo-doping.

アモルファス半導体の光誘起原子移動 --- フォトドーピングと光誘 起結晶化 ---　　　　　　　　　　　　　　　
井上 恒一, 松田理, 邑瀬 和生
固体物理別冊特集号「電子励起による非平衡ダイナミックス--- 新物質科学の創出に向け て ---」, 71, 78, 1993, [Peer-reviewed]
Japanese, Scientific journal

AlGaAs MBE growth and formation of quantum wire structures on vicinal GaAs (110) surfaces
Hisao Nakashima, Kenta Kimura, Masamichi Sato, Koichi Inoue, Kenzo Maehashi, Shigehiko Hasegawa, Masaaki Iwane, Osamu Matsuda, Kazuo Murase
Shinku, 36, 11, 862, 868, 1993, [Peer-reviewed]
English, Scientific journal, Quantum wire-like structures are formed in the AlGaAs/GaAs superlattices grown on vicinal GaAs (110) surfaces by MBE. SEM and EPMA observations reveal that the formation of giant steps and orientation dependent AlAs mole fraction of AlGaAs layers induce the quantum wire-like structures. Using RHEED, it is found that the step structures of AlGaAs surfaces depend on growth temperatures (diatomic steps above 600°C, giant steps below 600°C), while all the GaAs and AlAs surfaces consist of regular arrays of diatomic steps. Using this phenomenon, quantum wire structures are naturally formed by growing AlAs/AlGaAs/AlAs quantum wells on vicinal GaAs (110) surfaces with giant growth steps. The photoluminescence strongly polarized parallel to the wire direction gives a clear evidence for the formation of quantum wire structures. © 1993, The Vacuum Society of Japan. All rights reserved.

FORMATION AND PHOTOLUMINESCENCE OF QUANTUM WIRE STRUCTURES ON VICINAL (110) GAAS SUBSTRATES BY MBE
INOUE, K, KIMURA, K, MAEHASHI, K, HASEGAWA, S, NAKASHIMA, H, IWANE, M, MATSUDA, O, MURASE, K
Journal of Crystal Growth, 127, 1-4, 1041, 1044, ELSEVIER SCIENCE BV, 1993, [Peer-reviewed]
English, Scientific journal, Quantum wire structures are formed by the molecular beam epitaxial growth of AlAs-AlGaAs-AlAs quantum well on the large-growth-step structures of superlattices on vicinal (110) GaAs substrates. From the PL spectra, Al compositions in the wire are estimated to be much smaller than those in the well layers. The PL is polarized parallel to the wire direction. The observed large polarization supports the carrier confinement to the quantum wire structures.

INVERSE-PHOTOEMISSION STUDY OF THE CONDUCTION BANDS IN AMORPHOUS GESE2
HOSOKAWA, S, NISHIHARA, K, HARI, Y, TANIGUCHI, M, MATSUDA, O, MURASE, K
Physical Review B, 47, 23, 15509, 15514, 1993, [Peer-reviewed]
English, Scientific journal, The unoccupied electronic structure of amorphous GeSe2 has been investigated by means of inverse-photoemission spectroscopy. We have found prominent peaks at 2.1 and 4.7 eV above the Fermi level, and another weak and broad peak at about 8 eV. The energy positions of these peaks are consistent with those of the calculated density of states of conduction bands and those expected from the imaginary part of dielectric function obtained by the optical reflectance measurement. By comparison with the Ge 2p,3d, and Se 3d core-absorption spectra, the first and second peaks are assigned to the antibonding states of the Ge-Se covalent bonds, and the third peak corresponds to the 4d and/or 5s states of both the Ge and Se atoms. © 1993 The American Physical Society.

Structure and vibrational properties of amorphous germanium chalcogenide: medium range structure and light induced crystallization
Kazuo Murase, Osamu Matsuda, Koichi Inoue
固体物理, 27, 11, 841, 850, アグネ技術センタ-, 1992, [Peer-reviewed]
Japanese, Scientific journal

PHOTOLUMINESCENCE AND RAMAN-SCATTERING SPECTRA FROM POROUS SILICON
INOUE, K, MAEHASHI, K, NAKASHIMA, H, MATSUDA, O, MURASE, K
Superlattices and Microstructures, 12, 1, 77, 80, ACADEMIC PRESS LTD, 1992, [Peer-reviewed]
English, Scientific journal

SPECTRAL AND SPATIAL-BEHAVIOR OF RAMAN-SCATTERING AND PHOTOLUMINESCENCE FROM POROUS SILICON
INOUE, K, MATSUDA, O, MAEHASHI, K, NAKASHIMA, H, MURASE, K
Japanese Journal of Applied Physics Part 2-Letters, 31, 8A, L997, L1000, JAPAN J APPLIED PHYSICS, 1992, [Peer-reviewed]
English, Scientific journal, Depth profiles of Raman scattering and the photoluminescence (PL) properties of anodized porous Si have been studied by micro-measurement techniques. In Raman spectra a remarkable low-energy shift and broadening of the optical phonon line are observed as compared with the bulk Si phonon line basically owing to the phonon confinement. In the depth profiles the PL shows blueshift correlating with the low-energy shift of the Raman peak as the measured point approaches the surface. The redshift of the PL peak has been observed with the low-energy excitation in normal-incidence experiments. It is concluded that the structural depth inhomogeneity strongly affects the optical properties of porous Si.

DISORDER IN GESE2 SMALL CRYSTALS AND MEDIUM-RANGE STRUCTURE IN AMORPHOUS GESE2
MATSUDA, O, INOUE, K, NAKANE, T, MURASE, K
Journal of Non-Crystalline Solids, 150, 1-3, 202, 206, ELSEVIER SCIENCE BV, 1992, [Peer-reviewed]
English, Scientific journal, The Raman scattering spectra of various forms of GeSe2, such as amorphous films, single crystals, and small crystals prepared by a gas-evaporation deposition technique, are investigated with an excitation photon energy ranging from 2.1 to 2.8 eV. In the spectra of the crystals, there are two Raman bands, originating from two types of breathing vibrations of the GeSe4/2 tetrahedra: one is spread over the corner-sharing tetrahedra and the other is quasi-localized on the edge-sharing tetrahedra. In addition to the resonant Raman scattering related to the edge-sharing tetrahedra through the exciton transition observed with 2.71 eV excitation in the single crystals, a new resonant spectrum is found only in the small crystals with 2.54 eV excitation. With increasing disorder in the crystals, the intensity ratio between the two breathing vibration bands increases in the off-resonant excitation region. The Raman spectra in the amorphous states are ascribed to the breathing vibrations of GeSe4/2 tetrahedra which form a medium-range structure topologically similar to that of crystalline fragments.

A COMPARISON BETWEEN THE RAMAN MODES OF THE TETRAHEDRAL NETWORK IN AMORPHOUS AND LAYERED CRYSTALLINE GESE2
INOUE, K, MATSUDA, O, MURASE, K
Journal of Non-Crystalline Solids, 150, 1-3, 197, 201, ELSEVIER SCIENCE BV, 1992, [Peer-reviewed]
English, Scientific journal, The characteristic Al peak at 199 cm-1 and the A1C peak at 216 cm-1 in the Raman spectrum of amorphous GeSe2 were compared with the peaks at 211 and 216 cm-1 in the spectrum of crystalline GeSe2. It was proved that the crystalline 216 cm-1 peak is an intrinsic mode which is enhanced by the bulk exciton transition. From a model calculation using a valence force field and bond polarizability, the 211 cm-1 peak was assigned to in-phase breathing vibrations extended along the GeSe4 tetrahedral chain structure, while the 216 cm-1 peak was attributed to in-phase breathing vibrations quasi-localized at the GeSe4 edge-sharing tetrahedra. The phonon density of states in the crystal has a doublet peak similar to the amorphous Raman spectrum. A correspondence between the amorphous and the crystalline Raman spectra was proposed.

RAMAN-SPECTRA OF TETRAHEDRAL VIBRATIONS IN CRYSTALLINE GERMANIUM DICHALCOGENIDES, GES2 AND GESE2, IN HIGH AND LOW-TEMPERATURE FORMS
INOUE, K, MATSUDA, O, MURASE, K
Solid State Communications, 79, 11, 905, 910, PERGAMON-ELSEVIER SCIENCE LTD, 1991, [Peer-reviewed]
English, Scientific journal, Raman spectra of GeX2 (X = S and Se) crystals in high (HT) and low (LT) temperature forms have been studied on the view point of the connectivity of GeX4 tetrahedra. The characteristic Raman bands are understood by a simple valence-force-field model combined with a bond polarizability model. The most intense Raman bands in HT-GeX2 have been assigned to tetrahedral A1 vibrations extended in the chain structures along the [100] direction. Quasi-localized A1 vibrations in the bridge structures in HT-GeX2 are responsible for a higher side-band of the main band. The main bands in the spectra of LT-GeX2 have been assigned to nearly degenerated A1 vibrations linearly extended in the two chains along the [001] direction. The difference between the spectra of GeS2 and GeSe2 has been roughly explained to be due to the difference between atomic masses.

RESONANT RAMAN-STUDY ON CRYSTALLINE GESE2 IN RELATION TO AMORPHOUS STATES
MATSUDA, O, INOUE, K, MURASE, K
Solid State Communications, 75, 4, 303, 308, PERGAMON-ELSEVIER SCIENCE LTD, 1990, [Peer-reviewed]
English, Scientific journal

IDENTIFICATION OF THE A1 COMPANION RAMAN BAND BY 2-DIMENSIONAL MEDIUM RANGE STRUCTURE IN AMORPHOUS GESE2
O MATSUDA, K INOUE, K MURASE
20TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS, VOLS 1-3, 2135, 2138, WORLD SCIENTIFIC PUBL CO PTE LTD, 1990, [Peer-reviewed]
English, International conference proceedings

RAMAN AND PHOTOLUMINESCENCE INVESTIGATIONS OF ZNSE-ZNS STRAINED-LAYER SUPERLATTICES
SHON, LH, INOUE, K, MATSUDA, O, MURASE, K, YOKOGAWA, T, OGURA, M
Solid State Communications, 67, 8, 779, 782, PERGAMON-ELSEVIER SCIENCE LTD, 1988, [Peer-reviewed]
English, Scientific journal

2P1-9 Imaging surface acoustic waves on a metamaterial based on silica microspheres
Otsuka Paul H., Mezil Sylvain, Matsuda Osamu, Tomoda Motonobu, Gian Tian, Boechler Nicholas, Maznev Alex A., Fang Nicholas, Wright Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 36, "2P1, 9-1"-"2P1-9-2", 05 Nov. 2015
Steering committee of symposium on ultrasonic electronics, English

2E3-1 Extraordinary transmission of gigahertz surface acoustic waves
Sylvain Mezil, Kazuki Chonan, Sam H. Lee, Motonobu Tomoda, Osamu Matsuda, Paul H. Otsuka, Oliver B. Wright, Proceedings of Symposium on Ultrasonic Electronics, 36, "2E3, 1-1"-"2E3-1-2", 05 Nov. 2015
Steering committee of symposium on ultrasonic electronics, English

3P2-18 Imaging flexural waves in microscopic wedges(Poster Session)
Tomoda Motonobu, Matsueda Shinnosuke, Otsuka Paul H., Matsuda Osamu, Veres Istvan A., Gusev Vitali E., Wrigth Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 35, 451, 452, 03 Dec. 2014
Steering committee of symposium on ultrasonic electronics, English

2E1-1 Watching arbitrary acoustic whispering-gallery modes in the GHz range using ultrashort light pulses(Measurement techniques, Nondestructive Evaluation)
Mezil Sylvain, Otsuka Paul H., Kaneko Shogo, Wright Oliver B., Tomoda Motonobu, Matsuda Osamu, Proceedings of Symposium on Ultrasonic Electronics, 35, 183, 184, 03 Dec. 2014
Steering committee of symposium on ultrasonic electronics, English

2P1-10 Imaging localized phonon fields in phononic crystal slabs(Poster Session)
Otsuka P. H., Chinbe R., Kim S. H., Tomoda M., Matsuda O., Veres I. A., Tanaka Y., Jeon H. S., Wright O. B., Proceedings of Symposium on Ultrasonic Electronics, 35, 227, 228, 03 Dec. 2014
Steering committee of symposium on ultrasonic electronics, English

Time-resolved Two-dimensional Optical Imaging of GHz Surface Acoustic Waves and its Application
松田 理, ライト オリバー B., 非破壊検査, 63, 4, 195, 199, Apr. 2014
日本非破壊検査協会, Japanese

28aCK-8 Generation and detection of arbitrary frequency response in pump-probe measurement with periodic excitation
Matsuda Osamu, Kaneko Shogo, Tomoda Motonobu, Wright Oliver B., Meeting abstracts of the Physical Society of Japan, 69, 1, 748, 748, 05 Mar. 2014
The Physical Society of Japan (JPS), Japanese

Generation and observation of GHz-THz acoustic waves in thin films and microstructures using optical methods
Osamu Matsuda, Oliver B. Wright, Springer Series in Optical Sciences, 180, 129, 151, 2014
Springer Verlag, English, Book review

3P1-1 Imaging surface acoustic wave propagation in a triangular-lattice phononic crystal(Poster Session)
Otsuka Paul H., Chinbe Ryota, Tomoda Motonobu, Matsuda Osamu, Wright Oliver B., Veres Istvan, Lee Joo-Hyung, Yoon Jun-Bo, Proceedings of Symposium on Ultrasonic Electronics, 34, 413, 414, 20 Nov. 2013
Steering committee of symposium on ultrasonic electronics, English

1P2-34 Mechanical contacts mapped by picosecond ultrasonic pulses and non-equilibrium electrons(Poster Session)
Tomoda Motonobu, Dehoux Thomas, Iwasaki Yohei, Matsuda Osamu, Gusev Vitalyi E., Wright Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 34, 103, 104, 20 Nov. 2013
Steering committee of symposium on ultrasonic electronics, English

27pXG-4 Time-resolved two-dimensional imaging of GHz surface acoustic waves on phononic crystals
Matsuda Osamu, Meeting abstracts of the Physical Society of Japan, 68, 1, 763, 763, 26 Mar. 2013
The Physical Society of Japan (JPS), Japanese

1P1-6 Time-resolved imaging of negative refraction of surface acoustic waves in two-dimensional phononic crystals(Poster Session)
Koga Hiroaki, Tomoda Motonobu, Matsuda Osamu, Chinbe Ryota, Sakuma Hirotaka, Otsuka Paul H., Veres Istvan A., Wright Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 33, 29, 30, 13 Nov. 2012
Steering committee of symposium on ultrasonic electronics, English

2P2-7 Precise frequency control in the time-resolved 2D imaging of GHz surface acoustic waves(Poster Session)
Kaneko Shogo, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 33, 181, 182, 13 Nov. 2012
Steering committee of symposium on ultrasonic electronics, English

Optical tomographic imaging of picosecond pulses with 200nm spatial resolution
TOMODA Motonobu, MATSUO Hiroyuki, VOTI Roberto Li, MATSUDA Osamu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 33rd, 7, 8, 13 Nov. 2012
Steering committee of symposium on ultrasonic electronics, English

Time-resolved imaging of GHz surface acoustic waves in TeO2 through the photoelastic effect
UETSUJI Atsuki, MATSUDA Osamu, TOMODA Motonobu, SAKUMA Hirotaka, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 33rd, 41, 42, 13 Nov. 2012
Steering committee of symposium on ultrasonic electronics, English

Direct measurement of surface displacement of metal thin films in picosecond laser ultrasonics
KOIWA Shun, MATSUDA Osamu, BEARDSLEY Ryan, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 33rd, 305, 306, 13 Nov. 2012
Steering committee of symposium on ultrasonic electronics, English

ピコ秒領域表面変位測定によるWおよびCr薄膜中光励起電子の超高速緩和の研究
松田理, 小岩俊, BEARDSLEY Ryan, 友田基信, WRIGHT Oliver B, 日本物理学会講演概要集, 67, 2, 687, 687, 24 Aug. 2012
The Physical Society of Japan (JPS), Japanese

ピコ秒領域表面変位の直接測定による金属中光励起電子の超高速緩和の研究
松田理, 大野敦史, 小岩俊, 友田基信, WRIGHT Oliver B, 日本物理学会講演概要集, 67, 1, 814, 814, 05 Mar. 2012
The Physical Society of Japan (JPS), Japanese

Study of the generation and detection of GHz acoustic waves in a SiO2 film on a GaAs (411) substrate using picosecond laser acoustics
TONOMURA Masahiro, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 32nd, 177, 178, 08 Nov. 2011
Steering committee of symposium on ultrasonic electronics, English

Extraordinary optical transmission modulated by the vibrational modes of a periodic structure of square holes
SAKUMA Hirotaka, TOMODA Motonobu, MATSUDA Osamu, OTSUKA Paul H, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 32nd, 9, 10, 08 Nov. 2011
Steering committee of symposium on ultrasonic electronics, English

Ultrafast optical probing of the vibrations of gold nano-dishes
HOSHII Wataru, KELF Timothy A, COLE Robin M, VERES Istvan A, MAHAJAN Sumeet, BAUMBERG Jeremy J, TOMODA Motonobu, MATSUDA Osamu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 32nd, 63, 64, 08 Nov. 2011
Steering committee of symposium on ultrasonic electronics, English

1J1-1 Extraordinary optical transmission modulated by the vibrational modes of a periodic structure of square holes(Ultrasonic Properties of Materials, Phonon Physics, Acousto-optics)
Sakuma Hirotaka, Tomoda Motonobu, Matsuda Osamu, Otsuka Paul H, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 32, 9, 10, 08 Nov. 2011
Steering committee of symposium on ultrasonic electronics, English

2Pa1-4 Ultrafast optical probing of the vibrations of gold nano-dishes(Poster Session)
Hoshii Wataru, Kelf Timothy A, Cole Robin M, Veres Istvan A, Mahajan Sumeet, Baumberg Jeremy J, Tomoda Motonobu, Matsuda Osamu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 32, 63, 64, 08 Nov. 2011
Steering committee of symposium on ultrasonic electronics, English

2Pb1-1 Study of the generation and detection of GHz acoustic waves in a SiO_2 film on a GaAs (411) substrate using picosecond laser acoustics(Poster Session)
Tonomura Masahiro, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 32, 177, 178, 08 Nov. 2011
Steering committee of symposium on ultrasonic electronics, English

3Pa1-5 Imaging Lamb waves in a phononic crystal waveguide(Poster Session)
Chinbe R, Kim S. H, Otsuka P. H, Tomoda M, Matsuda O, Veres I. A, Tanaka Y, Jeon H. S, Wright O. B, Proceedings of Symposium on Ultrasonic Electronics, 0, 32, 325, 326, 08 Nov. 2011
Steering committee of symposium on ultrasonic electronics, English

OS02-2-3 Optical tomographic imaging of nanometer ultrasonic pulses propagation
Tomoda Motonobu, Matsuo Hiroyuki, Matsuda Osamu, Wright Oliver B., Voti Roberto Li, Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics, 2011, 10, "OS02, 2-3-1", 19 Sep. 2011
The Japan Society of Mechanical Engineers, English

26aHC-11 Direct measurement of ultrafast surface displacement in picosecond laser acoustics
Matsuda Osamu, Ohno Atsushi, Tomoda Motonobu, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 66, 1, 773, 773, 03 Mar. 2011
The Physical Society of Japan (JPS), Japanese

Dynamic imaging of surface acoustic waves in phononic crystals
Oliver B. Wright, Istvan A. Veres, Dieter M. Profunser, Osamu Matsuda, Brian Culshaw, Udo Lang, SMART NANO-MICRO MATERIALS AND DEVICES, 8204, ROMBUNNO.17A-R-10, 2011
Using ultrashort pulsed optical excitation and interferometric detection, we image ultrahigh- frequency surface acoustic waves on two-dimensional (2D) phononic crystals in the time domain. The samples consist of a square lattice of air-filled holes etched in a silicon substrate. Good agreement with time-domain finite element numerical simulations is obtained. The dispersion relation is derived and stop bands are revealed by means of Fourier transforms. The wave fields corresponding to acoustic eigenmodes at specific frequencies are also presented., SPIE-INT SOC OPTICAL ENGINEERING, English

Time resolved 2-dimensional acoustic wave imaging with photoelastic effect in GHz frequency range
Osamu Matsuda, Taiki Saito, Motonobu Tomoda, Oliver B. Wright, Ultrasonic technology, 23, 1, 69, 73, 2011, [Invited], [Lead author, Corresponding author]
日本工業出版, Japanese, Introduction scientific journal

Two-dimensional imaging of surface acoustic waves and photoluminescence on GaAs
KANEKO Shogo, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 31st, 159, 160, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

Imaging GHz surface acoustic waves on anisotropic media through the photoelastic effect
SAITO Taiki, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 31st, 447, 448, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

Study of ultrafast electron relaxation by the direct measurement of picosecond surface displacement
OHNO Atsushi, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 31st, 33, 34, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

Visualization of Propagating Picosecond Ultrasonic Pulses in Transparent Solids
MATSUO Hiroyuki, TOMODA Motonobu, LI, VOTI Robert, MATSUDA Osamu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 31st, 161, 162, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

Time-resolved two-dimensional imaging of surface acoustic waves generated by optical pulses focused to arbitrary spatial shapes
SUGAHARA Hiroyuki, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, GLORIEUX Christ,CLARK Matt, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 31st, 23, 24, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

Acoustic Modes of GaAs Nanopillars Studied with Ultrashort Optical Pulses
SAKUMA Hirotaka, TOMODA Motonobu, MATSUDA Osamu, FUKUI Takashi, TOMIOKA Katsuhiro,VERES Istvan A, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 31st, 153, 154, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

1Pa-4 Time-resolved two-dimensional imaging of surface acoustic waves generated by optical pulses focused to arbitrary spatial shapes(Poster Session)
Sugahara Hiroyuki, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Glorieux Christ, Clark Matt, Proceedings of Symposium on Ultrasonic Electronics, 0, 31, 23, 24, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

1Pa-9 Study of ultrafast electron relaxation by the direct measurement of picosecond surface displacement(Poster Session)
Ohno Atsushi, Matsuda Osamu, Tomoda Motonobu, Wrieht Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 31, 33, 34, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

1Pb-6 Acoustic Modes of GaAs Nanopillars Studied with Ultrashort Optical Pulses(Poster Session)
Sakuma Hirotaka, Tomoda Motonobu, Matsuda Osamu, Fukui Takashi, Tomioka Katsuhiro, Veres Istvan A, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 31, 153, 154, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

1Pb-9 Two-dimensional imaging of surface acoustic waves and photoluminescence on GaAs(Poster Session)
Kaneko Shogo, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 31, 159, 160, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

1Pb-10 Visualization of Propagating Picosecond Ultrasonic Pulses in Transparent Solids(Poster Session)
Matsuo Hiroyuki, Tomoda Motonobu, Li Voti Roberto, Matsuda Osamu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 31, 161, 162, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

3J-2 Imaging GHz surface acoustic waves on anisotropic media through the photoelastic effect(Measurement Techniques)
Saito Taiki, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 31, 447, 448, 06 Dec. 2010
Steering committee of symposium on ultrasonic electronics, English

24pRC-12 プラズモニック構造におけるGHzフォノンイメージング(24pRC 超高速現象,領域5(光物性))
WRIGHT O. B., KELF T., MATSUDA O., COLE R., MAHAJAN S., BAUMBERG J. J., VERES I. A., 日本物理学会講演概要集, 65, 2, 700, 700, 18 Aug. 2010
一般社団法人日本物理学会, English

25pRE-4 Time-resolved imaging of GHz surface acoustic waves using the photoelastic effect
Matsuda Osamu, Saito Taiki, Tomoda Motonobu, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 65, 2, 723, 723, 18 Aug. 2010
The Physical Society of Japan (JPS), Japanese

20aHQ-9 Direct measurement of the ultrafast surface displacement in picosecond laser acoustics
Matsuda Osamu, Ohno Atsushi, Tomoda Motonobu, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 65, 1, 735, 735, 01 Mar. 2010
The Physical Society of Japan (JPS), Japanese

Time-resolved imaging of surface acoustic waves on GaAs
KANEKO Shogo, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 30th, 469, 470, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

Imaging GHz surface acoustic waves through the photoelastic effect
SAITO Taiki, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 30th, 59, 60, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

Direct measurement of surface displacement in picosecond laser ultrasonics
OHNO Atsushi, MATSUDA Osamu, TOMODA Motonobu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 30th, 221, 222, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

Vibrations of nanostructures probed by ultrashort optical pulses
SAKUMA Hirotaka, TOMODA Motonobu, MATSUDA Osamu, FUKUI Takashi, TOMIOKA Katsuhiro, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 30th, 209, 210, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

Time-resolved imaging of confined Rayleigh and Lamb waves in microscopic resonators and wedges
TOMODA Motonobu, MATSUEDA Shinnosuke, WRIGHT, Oliver B, MATSUDA Osamu, NISHIJIMA Yoshiaki, UENO Kosei, SAULIUS Juodkazis, MISAWA Hiroaki, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 30th, 457, 458, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

1P2-22 Imaging GHz surface acoustic waves through the photoelastic effect(Poster Session)
Saito Taiki, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Symposium on ultrasonic electronics, 0, 30, 59, 60, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

2P1-4 Vibrations of nanostructures probed by ultrashort optical pulses(Poster Session)
Sakuma Hirotaka, Tomoda Motonobu, Matsuda Osamu, Fukui Takashi, Tomioka Katsuhiro, Wright Oliver B, Symposium on ultrasonic electronics, 0, 30, 209, 210, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

2P1-10 Direct measurement of surface displacement in picosecond laser ultrasonics(Poster Session)
Ohno Atsushi, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Symposium on ultrasonic electronics, 0, 30, 221, 222, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

3J1-4 Time-resolved imaging of surface acoustic waves on two-dimensional phononic crystal waveguides(Physical Acoustics, Acousto-Optics)
Nanri Keisuke, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Profunser Dieter, Khelif Abdelkrim, Laude Vincent, Benchabane Sarah, Symposium on ultrasonic electronics, 0, 30, 415, 416, 18 Nov. 2009
Surface acoustic wave propagation at frequencies up to 1GHz is imaged in the time domain on several two-dimensional phononic crystal waveguides by means of ultrashort pulsed optical excitation and detection. These images are Fourier Transformed and analyzed., Steering committee of symposium on ultrasonic electronics, Japanese

3P1-18 Time-resolved imaging of confined Rayleigh and Lamb waves in microscopic resonators and wedges(Poster Session)
Tomoda Motonobu, Matsueda Shinnosuke, Wright Oliver B, Matsuda Osamu, Nishijima Yoshiaki, Ueno Kosei, Saulius Juodkazis, Misawa Hiroaki, Symposium on ultrasonic electronics, 0, 30, 457, 458, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

3P1-24 Time-resolved imaging of surface acoustic waves on GaAs(Poster Session)
Kaneko Shogo, Matsuda Osamu, Tomoda Motonobu, Wright Oliver B, Symposium on ultrasonic electronics, 0, 30, 469, 470, 18 Nov. 2009
Steering committee of symposium on ultrasonic electronics, English

30pRB-2 Imaging of picosecond phonon pulses by use of optical tomography
Tomoda Motonobu, Voti Roberto Li, Matsuda Osamu, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 64, 1, 978, 978, 03 Mar. 2009
The Physical Society of Japan (JPS), Japanese

30pRB-11 A study on acoustic wave propagation on liquid surface
Matsuda O, Cote Renaud, Glorieux Christ, Meeting abstracts of the Physical Society of Japan, 64, 1, 980, 980, 03 Mar. 2009
The Physical Society of Japan (JPS), Japanese

Observation of vibrational mode of nanoscale semiconductor pillar
Hirotaka Sakuma, Motonobu Tomoda, Osamu Matsuda, Takashi Fukui, Katsuhiro Tomioka, Oliver B. Wright, Ultrasonic technology, 21, 6, 64, 67, 2009
日本工業出版, Japanese, Introduction scientific journal

Imaging the Acoustic Rectification of Surface Acoustic Waves
DANWORAPHONG Sorasak, KELF, Timothy A, MATSUDA Osamu, WRIGHT Oliver B, UENO Kosei, NISHIJIMA Yoshiaki, JUODKAZIS Saulius, MISAWA Hiroaki, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 29th, 179, 180, 11 Nov. 2008
Steering committee of symposium on ultrasonic electronics, English

Real time imaging and dispersion behavior of Lamb waves in an elastic wedge
MATSUEDA Shinnosuke, TOMODA Motonobu, MATSUDA Osamu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 29th, 381, 382, 11 Nov. 2008
Steering committee of symposium on ultrasonic electronics, English

Real-time imaging of GHz acoustic waves on bulk acoustic resonators
FUJIKURA Takashi, MATSUDA Osamu, WRIGHT Oliver B, MASSON Jeremy, BALLANDRAS Sylvain, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 29th, 379, 380, 11 Nov. 2008
Steering committee of symposium on ultrasonic electronics, English

1J2a-3 Vibrational modes of semiconductor nanopillars studied by picosecond ultrasonics(Measurement techniques)
Sakuma Hirotaka, Tomoda Motonobu, Matsuda Osamu, Fukui Takashi, Tomioka Katsuhiro, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 29, 19, 20, 11 Nov. 2008
We investigate the vibrational modes of GaAs nanopillars of hexagonal cross section on a GaAs substrate using an ultrafast optical technique. The motions of the pillars after excitation with visible light pulses are detected using a time-delayed infrared light pulses. Thickness modes of the pillars are detected in the 10-30 GHz range., Steering committee of symposium on ultrasonic electronics, Japanese

2E2b Imaging the Acoustic Rectification of Surface Acoustic Waves(Aural English Session I)
Danworaphong Sorasak, Kelf Timothy A, Matsuda Osamu, Wright Oliver B, Ueno Kosei, Nishijima Yoshiaki, Juodkazis Saulius, Misawa Hiroaki, Proceedings of Symposium on Ultrasonic Electronics, 0, 29, 179, 180, 11 Nov. 2008
Steering committee of symposium on ultrasonic electronics, English

3P2b-8 Real time imaging and dispersion behavior of Lamb waves in an elastic wedge(Poster Session)
Matsueda Shinnosuke, Tomoda Motonobu, Matsuda Osamu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 29, 381, 382, 11 Nov. 2008
Steering committee of symposium on ultrasonic electronics, English

22aPS-50 Acoustic waves on liquid surface studied by heterodyne diffraction method
Matsuda O, Glorieux Christ, Meeting abstracts of the Physical Society of Japan, 63, 2, 661, 661, 25 Aug. 2008
The Physical Society of Japan (JPS), Japanese

24aYJ-12 Light scattering by picosecond acoustic waves propagating in anisotropic medium
Matsuda O, Wright Oliver B, Hurley David H, Gusev Vitalvi, Shimizu K, Meeting abstracts of the Physical Society of Japan, 63, 1, 718, 718, 29 Feb. 2008
The Physical Society of Japan (JPS), Japanese

SPATIOTEMPORAL MAPPING OF SYMMETRICAL SURFACE ACOUSTIC FIELDS ON CRYSTALS AND PERIODIC MICROSTRUCTURES　　　　　　　　　　　　　　　
T. Tachizaki, O. B. Wright, O. Matsuda, Topological Aspects of Critical Systems and Networks, 249, 252, Jun. 2007, [Peer-reviewed]
English, Introduction international proceedings

19pXB-9 Spatiotemporal imaging of MHz surface phonon whispering gallery modes and their analysis in Fourier space
Tachizaki Takehiro, Matsuda Osamu, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 62, 1, 958, 958, 28 Feb. 2007
The Physical Society of Japan (JPS), Japanese

18aXA-5 Acoustic wave propagation in a medium with depth-dependent inhomogeneity
Matsuda O, Glorieux Christ, Meeting abstracts of the Physical Society of Japan, 62, 1, 931, 931, 28 Feb. 2007
The Physical Society of Japan (JPS), Japanese

Imaging the propagation of a gigahertz ultrasonic pulse in a transparent medium
TOMODA Motonobu, VOTI Roberto Li, MATSUDA Osamu, WRIGHT Oliver B, 超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集, 27th, 183, 184, 15 Nov. 2006
Steering committee of symposium on ultrasonic electronics, English

Imaging ripples on phononic crystals reveals acoustic band structure and bloch harmonics (vol 97, pg 055502, 2006)
Dieter M. Profunser, Oliver B. Wright, Osamu Matsuda, PHYSICAL REVIEW LETTERS, 97, 11, Sep. 2006
AMERICAN PHYSICAL SOC, English, Others

Real Time Imaging Techniques for Surface Waves on Topological Structures　　　　　　　　　　　　　　　
T. Tachizaki, T. Muroya, O. Matsuda, O. B. Wright, Topology in Ordered Phases, 323, 326, Aug. 2006, [Peer-reviewed]
English, Introduction international proceedings

28pYA-2 Real-time 2D imaging of a surface phonon whispering gallery mode in a microstructure
Tachizaki Takehiro, Matsuda Osamu, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 61, 1, 940, 940, 04 Mar. 2006
The Physical Society of Japan (JPS), Japanese

P3-43 Real time imaging of surface acoustic waves by means of the photoelastic effect
Kawada Kenji, Tachizaki Takehiro, Matsuda Osamu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 26, 425, 426, 16 Nov. 2005
Steering committee of symposium on ultrasonic electronics, Japanese

21aYD-7 Picosecond acoustic phonon pulses generated and detected with ultrashort optical pulses
Matsuda Osamu, Meeting abstracts of the Physical Society of Japan, 60, 2, 610, 610, 19 Aug. 2005
The Physical Society of Japan (JPS), English

Picosecond acoustics in semiconductor quantum wells
Matsuda O, Tachizaki T, Fukui T, Baumberg JJ, Wright OB, Ultrafast Phenomena in Semiconductors and Nanostructure Materials IX, 5725, 257, 264, 22 Jul. 2005, [Peer-reviewed]
Picosecond acoustic phonon pulses are generated with ultrashort laser pulses in a sample containing three GaAs-Al0.3Ga0.7As quantum wells of different thickness. The pump photon energy is tuned through the hh1-e1 transitions of each well (1.44 - 1.64 eV) and the probe photon energy is chosen to allow detection of the phonon pulses at the sample surface (3.06 eV). Transient optical reflectance and phase changes are recorded as a function of the delay time between the pump and probe light pulses using an interferometric technique. The transition between the valence and conduction sublevels of the wells is observed to strongly influence the pump-photon-energy dependence of the acoustic phonon pulse generation. The data are analyzed with a model that relates the carrier wavefunctions in the quantum wells to the acoustic strain through the deformation potential, and the acoustic strain to the transient optical reflectance and phase.

Acoustic phonon generation and detection in GaAs/Al0.3Ga0.7As quantum wells with picosecond laser pulses (vol B 71, art no 115330, 2005)
O Matsuda, T Tachizaki, T Fukui, JJ Baumberg, OB Wright, PHYSICAL REVIEW B, 71, 15, Apr. 2005
AMERICAN PHYSICAL SOC, English, Others

Evaluation of vapour-deposited ice films with laser picosecond acoustics
KASHIWADA Saori, MATSUDA Osamu, BAUMBERG Jeremy J, WRIGHT Oliver B, 応用物理学関係連合講演会講演予稿集, 52nd, 1, 475, 29 Mar. 2005
English

25aXP-9 Detection of picosecond shear acoustic phonon pulses in anisotropic materials
Matsuda O, Hurley David H, Gusev Vitalyi E, Shimizu K, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 60, 1, 691, 691, 04 Mar. 2005
The Physical Society of Japan (JPS), Japanese

G-1 Generation and detection of picosecond shear strain pulses with ultrashort light pulses(Photoacoustics, Acousto-optics)
Matsuda Osamu, Wright Oliver B., Hurley David H., Gusev Vitalyi E., Shimizu Kenichi, Proceedings of Symposium on Ultrasonic Electronics, 25, 315, 316, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, English

P2-46 Real time imaging of surface acoustic waves on a sphere(Short presentation for poster)
Yamazaki Hiroto, Matsuda Osamu, Wright Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 25, 249, 250, 27 Oct. 2004
In summary, we have demonstrated the real-time imaging of surface acoustic waves on isotropic spheres using an ultrafast optical technique. This method can be applied in future to anisotropic balls to investigate the effect of surface curvature and anisotropic propagation effects., Steering committee of symposium on ultrasonic electronics, English

E-2 Evaluation of ice films by picosecond acoustics(Fundamentals, Surface wave devices)
Kashiwada Saori, Matsuda Osamu, Baumberg Jeremy J., Wright Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 25, 299, 300, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, English

P2-42 Imaging of picosecond longitudinal acoustic pulses in a transparent medium(Short presentation for poster)
Tomoda Motonobu, Voti Roberto Li, Matsuda Osamu, Wright Oliver B., Proceedings of Symposium on Ultrasonic Electronics, 25, 241, 242, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, English

P2-45 Terahertz ultrasonic generation and detection in GaAs/AlGaAs quantum wells(Short presentation for poster)
Tachizaki T., Matsuda O., Fukui T., Baumberg J. J., Wright O. B., Proceedings of Symposium on Ultrasonic Electronics, 25, 247, 248, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, English

B-4 Surface acoustic wave imaging on periodic microstructures
Muramoto Eiji, Wright Oliver B, Matsuda Osamu, Tomoda Motonobu, Takezaki Taiichi, Sueoka Kazuhisa, Proceedings of Symposium on Ultrasonic Electronics, 0, 25, 11, 12, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, Japanese

P1-37 Imaging of surface acoustic waves on crystals through the photoelastic effect
Kawada Kenji, Tachizaki Takehiro, Yamazaki Hiroto, Matsuda Osamu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 25, 85, 86, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, Japanese

P1-54 Ultrafast dynamics of photoexcited carriers in GaAs investigated by picosecond acoustics
Sasajima Takashi, Tachizaki Takehiro, Matsuda Osamu, Akabori Masashi, Fukui Takashi, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 25, 119, 120, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, Japanese

P1-55 Direct measurement of ultrafast surface displacements with laser picosecond ultrasonics
Aoki Kae, Matsuda Osamu, Tachizaki Takehiro, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 25, 121, 122, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, Japanese

P1-58 Enhancement of ultrafast reflectivity changes due to ultrasonic wave propagation in a photonic band gap structure
Mizunuma Eitaro, Matsuda Osamu, Wright Oliver B, Proceedings of Symposium on Ultrasonic Electronics, 0, 25, 127, 128, 27 Oct. 2004
Steering committee of symposium on ultrasonic electronics, Japanese

12pXC-12 Spectral analysis of picosecond acoustic pulses
Tachizaki Takehiro, Saito Takahiro, Matsuda Osamu, Baumberg Jeremy J, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 59, 2, 639, 639, 25 Aug. 2004
The Physical Society of Japan (JPS), Japanese

12pXC-13 Direct measurement of picosecond transient surface displacement by an interferometer with obliquely incident probe light
Matsuda O, Aoki K, Tachizaki T, Wright O. B, Meeting abstracts of the Physical Society of Japan, 59, 2, 640, 640, 25 Aug. 2004
The Physical Society of Japan (JPS), Japanese

12aTJ-1 Imaging of picosecond acoustic pulse propagation in transparent material
Tomoda M, Voti Roberto Li, Matsuda O, Wright Oliver B, Meeting abstracts of the Physical Society of Japan, 59, 2, 850, 850, 25 Aug. 2004
The Physical Society of Japan (JPS), Japanese

12aTJ-2 Real-time imaging of GHz surface acoustic waves by ultrashort light pulses
Muroya T, Tachizaki T, Matsuda O, Wright O. B, Meeting abstracts of the Physical Society of Japan, 59, 2, 850, 850, 25 Aug. 2004
The Physical Society of Japan (JPS), Japanese

Picosecond acoustic phonon pulse generation in nickel and chromium (vol B 67, art no 205421, 2003)
T Saito, O Matsuda, OB Wright, PHYSICAL REVIEW B, 69, 23, Jun. 2004
AMER PHYSICAL SOC, English, Others

27aXM-9 Real-time imaging of surface acoustic waves propagating across the grain boundaries of polycrystalline cupper
Sugawara Y, Hurley Davd. H, Matsuda O, Wright Oliver. B, Suzuki T, Tamura S, Meeting abstracts of the Physical Society of Japan, 59, 1, 940, 940, 03 Mar. 2004
The Physical Society of Japan (JPS), Japanese

Probing electron wavefunctions in quantum wells using ultrafast coherent acoustic phonon generation
O. B. Wright, T. Tachizaki, O. Matsuda, T. Fukui, J. J. Baumberg, OSA Trends in Optics and Photonics Series, 97, 157, 01 Jan. 2004
Individual quantum wells in GaAs/AlGaAs heterostructures are selectively excited by ultrashort wavelength-tunable optical pulses. We demonstrate how the electron and hole wavefunctions can be probed from the generated coherent acoustic phonon pulses. © 2002 Optical Society of America.

P1-A-4 Real time imaging of surface acoustic waves
Wright Oliver B, Sugawara Yoshihiro, Matsuda Osamu, Proceedings of Symposium on Ultrasonic Electronics, 0, 24, 13, 14, 12 Nov. 2003
Steering committee of symposium on ultrasonic electronics, Japanese

Coherent TA phonon pulse generation and detection in laser picosecond ultrasonics
Matsuda O, Hurley D. H, Shimizu K, Wright O. B, Meeting abstracts of the Physical Society of Japan, 58, 2, 628, 628, 15 Aug. 2003
The Physical Society of Japan (JPS), Japanese

Ultrafast carrier dynamics in GaAs air gap structure probed by picosecond phonon pulses
Matsuda O, Fukui T, Akabori M, Wright Oliver. B, Meeting abstracts of the Physical Society of Japan, 58, 1, 679, 679, 06 Mar. 2003
The Physical Society of Japan (JPS), Japanese

P2-20 Cantilever dynamics in optical heterodyne force microscopy
Tomoda Motonobu, Matsuda Osamu, Wright Oliver B, Symposium on ultrasonic electronics, 0, 23, 179, 180, 07 Nov. 2002
Steering committee of symposium on ultrasonic electronics, Japanese

Laser picosecond acoustics with oblique probe light incidence
Matsuda O., Tachizaki T., Hurley D.H., Wright O. B., Meeting abstracts of the Physical Society of Japan, 57, 2, 638, 638, 13 Aug. 2002
The Physical Society of Japan (JPS), Japanese

Real time imaging and dispersion of surface phonons propagating on opaq〓e substrates
Sugawara Y., Matsuda O., Wright O.B., Meeting abstracts of the Physical Society of Japan, 57, 2, 790, 790, 13 Aug. 2002
The Physical Society of Japan (JPS), Japanese

27aYE-5 Analysis of laser picosecond acoustics signals in arbitrary transparent and opaque multilayer thin films
Matsuda O., Wright O. B., Meeting abstracts of the Physical Society of Japan, 57, 1, 712, 712, 01 Mar. 2002
The Physical Society of Japan (JPS), Japanese

P2-29 Cantilever dynamics in ultrasonic force microscopy
Matsuda Osamu, Terada Takuya, Inagaki Katsuhiko, Wright Oliver B, Symposium on ultrasonic electronics, 0, 22, 229, 230, 07 Nov. 2001
Steering committee of symposium on ultrasonic electronics, Japanese

H-5 2D Real Time Imaging of Surface Acoustic Waves in Isotropic and Anisotropic Materials
Sugawara Y, Matsuda O, Wright Oliver B, Symposium on ultrasonic electronics, 0, 22, 393, 394, 07 Nov. 2001
Steering committee of symposium on ultrasonic electronics, Japanese

Picosecond acoustic-phonon pulse generation mechanisms in transition metals
Saito T., Matsuda O., Wright O. B., Meeting abstracts of the Physical Society of Japan, 56, 2, 568, 568, 03 Sep. 2001
The Physical Society of Japan (JPS), Japanese

Ultrafast nonequilibrium relaxation dynamics of electrons in the transition metal Cr with 20 fs time resolution
Hirori H., Matsuda O., Wright O. B., Meeting abstracts of the Physical Society of Japan, 56, 2, 568, 568, 03 Sep. 2001
The Physical Society of Japan (JPS), Japanese

Wavelength selective light pulse excitation of picosecond acoustic phonon pulses in GaAs/Al_<0.3>Ga_<0.7>As quantum well structure
Matsuda O, Ishii I, Fukui T, Baumberg J. J, Wright O. B, Meeting abstracts of the Physical Society of Japan, 56, 2, 550, 550, 03 Sep. 2001
The Physical Society of Japan (JPS), Japanese

17aRE-12 Ultrashort timescale carrier diffusion in GaAs probed with picosecond acoustic pulses
Wright O. B, Perrin B, Matsuda O, Gusev V. E, Meeting abstracts of the Physical Society of Japan, 56, 2, 568, 568, 03 Sep. 2001
The Physical Society of Japan (JPS), English

Structural relaxations and network modifications in Ge-Se glasses
Nakaoka T., Wang Y., Matsuda O., Inoue K., Murase K., Meeting abstracts of the Physical Society of Japan, 55, 1, 608, 608, 10 Mar. 2000
The Physical Society of Japan (JPS), Japanese

Raman scattering investigation of the structure of amorphous silicon in a-Si/SiO_2 superlattice films
Wang Y., Matsuda O., Murase K., Meeting abstracts of the Physical Society of Japan, 55, 1, 608, 608, 10 Mar. 2000
The Physical Society of Japan (JPS), Japanese

27aC-6 Structure and low-frequency modes of Ge-(S, Se)bulk glasses
Murakami H, Nakaoka T, Nkamura M, Wang Y, Matsuda O, Inoue K, Murase K, Meeting abstracts of the Physical Society of Japan, 54, 2, 618, 618, 03 Sep. 1999
The Physical Society of Japan (JPS), Japanese

27aC-5 Resonant Raman scattering of glassy GoSe_2 and the local structures
Nakaoka T, Wang Y, Matsuda O, Inoue K, Murase K, Meeting abstracts of the Physical Society of Japan, 54, 2, 618, 618, 03 Sep. 1999
The Physical Society of Japan (JPS), Japanese

29p-ZF-5 Photoluminescence of amrophous GeSe_2 films
Komamine T., Y Wang., Nakaoka T., Matsuda O, Murase K., Meeting abstracts of the Physical Society of Japan, 54, 1, 156, 156, 15 Mar. 1999
The Physical Society of Japan (JPS), Japanese

29p-ZF-6 Resonance Raman scattering of crystalline GeSe_2 and assignments of the phonon modes
Nakaoka T., Y Wang, Matsuda O., Inoue K., Murase K., Meeting abstracts of the Physical Society of Japan, 54, 1, 156, 156, 15 Mar. 1999
The Physical Society of Japan (JPS), Japanese

Time resolved photoluminescence in crystalline GeSe_2
NAKAOKA T., WANG Y., MATSUOKA O., MURASE K., Meeting abstracts of the Physical Society of Japan, 53, 2, 173, 173, 05 Sep. 1998
The Physical Society of Japan (JPS), Japanese

Selective site occupation of chalcogen atoma in Ge-S-Se ternary glasses
NAKAMURA M., WANG Y., MATSUDA O., MURASE K., Meeting abstracts of the Physical Society of Japan, 53, 2, 175, 175, 05 Sep. 1998
The Physical Society of Japan (JPS), Japanese

Rigidity percolation of glassy Ge-(Se,S) system
WANG Y., NAKAMURA M., MATSUDA O., MURASE K., Meeting abstracts of the Physical Society of Japan, 53, 2, 175, 175, 05 Sep. 1998
The Physical Society of Japan (JPS), Japanese

Optical properties of Zn_<1-x>Mn_xS microcrystals
HANZAWA H., NAKAMURA Y., KOBAYASHI M., ENDO S., MATSUDA O., MURASE K., GLRIAT W., Meeting abstracts of the Physical Society of Japan, 53, 1, 142, 142, 10 Mar. 1998
The Physical Society of Japan (JPS), Japanese

Intertetrahedral interaction of Ge(S_xSe_<1-x>)_2 glasses
NAKAMURA M., MATSUDA O., MURASE K., Meeting abstracts of the Physical Society of Japan, 53, 1, 146, 146, 10 Mar. 1998
The Physical Society of Japan (JPS), Japanese

Time resolved photoluminescence measurement on glassy GeSe_2 : Excitation energy dependence
SAITOH Y., YAMAGATA K., MATSUDA O., MURASE K., Meeting abstracts of the Physical Society of Japan, 53, 1, 145, 145, 10 Mar. 1998
The Physical Society of Japan (JPS), Japanese

Time-resolved photoluminescence of GeSe_2 glass : Temperature dependence
YAMAGATA K., SAITOH Y., MATSUDA O., MURASE K., Meeting abstracts of the Physical Society of Japan, 53, 1, 145, 145, 10 Mar. 1998
The Physical Society of Japan (JPS), Japanese

Temperature dependence on low-energy excitation in Ramnan spectra of glassy Ge_xSe_<1-x>
WANG Y., NAKAMURA M., MATSUDA O., MURASE K., Meeting abstracts of the Physical Society of Japan, 53, 1, 146, 146, 10 Mar. 1998
The Physical Society of Japan (JPS), Japanese

Direct deposition of silicon and silicon-oxide films using low-energy Si focused ion beams
Yanagisawa J., Nakayama H., Matsuda O., Report,Research Center for Materials Science at Extreme Conditions,Osaka University, 2, 275, 278, Mar. 1998
大阪大学極限科学研究センタ-, English

6p-YL-10 The correlation of the low frequency vibrational properties and rigidity percolation phenomena in Ge_xSe_<1-x>glasses
Nakamura M, Matsuda O, Murase K, Meeting abstracts of the Physical Society of Japan, 52, 2, 767, 767, 16 Sep. 1997
The Physical Society of Japan (JPS), Japanese

29a-S-7 The dependence of the recrystallization temperature on the sample preparation methods in non-crystalline GeSe_2
Takeuchi H, Matsuda O, Murase K, Meeting abstracts of the Physical Society of Japan, 52, 1, 163, 163, 17 Mar. 1997
The Physical Society of Japan (JPS), Japanese

29a-S-8 Structural relaxation of g-Ge_xSe_<1-x> at glass-transition
Wang Y, Matsuda O, Yamamuro O, Matsuo T, Murase K, Meeting abstracts of the Physical Society of Japan, 52, 1, 163, 163, 17 Mar. 1997
The Physical Society of Japan (JPS), Japanese

29a-S-9 Low-frequency Raman scattering of Ge_xSe_<1-x> glasses
Nakamura M, Matsuda O, Inoue K, Murase K, Meeting abstracts of the Physical Society of Japan, 52, 1, 163, 163, 17 Mar. 1997
The Physical Society of Japan (JPS), Japanese

Crystalline phases around X=0.07 in Ge_XSe_<1-X>
Wang Y., Saito Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1996, 2, 156, 156, 13 Sep. 1996
The Physical Society of Japan (JPS), Japanese

Ion-lattice interactrion in Eu^<3+> doped GeS_2 glasses
Nakamura M., Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1996, 2, 155, 155, 13 Sep. 1996
The Physical Society of Japan (JPS), Japanese

Resonant Raman spectra of crystalline GeSe_2.
Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1996, 2, 155, 155, 13 Sep. 1996
The Physical Society of Japan (JPS), Japanese

31p-F-8 Time Resolved photoluminescence measurement on glassy GeSe_2.
Matsuda O., Wada Y., Saitoh Y., Yamagata K., Wang Y., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 51, 2, 135, 135, 15 Mar. 1996
The Physical Society of Japan (JPS), Japanese

31p-F-10 Temperature dependence of Raman spectra in glassy Ge_XSe_<1-X>
Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 51, 2, 135, 135, 15 Mar. 1996
The Physical Society of Japan (JPS), Japanese

31p-F-12 Network dimensionality and fractality of Ge-(S, Se) bulk glasses
Nakamura M., Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 51, 2, 136, 136, 15 Mar. 1996
The Physical Society of Japan (JPS), Japanese

31p-F-11 Excitaion energy dependence of photoluminescence spectra in glassy-Ge(S_xSe_<1-x>)_2
Wada Y., Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 51, 2, 136, 136, 15 Mar. 1996
The Physical Society of Japan (JPS), Japanese

29p-X-11 Photoemission, inverse-photoemission, and Raman spectra of amorphous Ge-Se-Bi films.
Matsuda O., Ohba T., Ono I., Grekos P., Kouchi T., Ueda C., Tamura M., Namatame H., Hosokawa S., Taniguchi M., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1995, 2, 186, 186, 12 Sep. 1995
The Physical Society of Japan (JPS), Japanese

29p-X-12 Excitation energy dependence of photoluminescence in glassy-Ge(S_xSe_<1-x>)_2
Wada Y., Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1995, 2, 187, 187, 12 Sep. 1995
The Physical Society of Japan (JPS), Japanese

29p-X-10 Raman scattering measurement of glass transition in GeSe_2
Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1995, 2, 186, 186, 12 Sep. 1995
The Physical Society of Japan (JPS), Japanese

29p-X-13 Temperature dependence of floppy mode in Ge-Se bulk glasses
Nakamura M., Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1995, 2, 187, 187, 12 Sep. 1995
The Physical Society of Japan (JPS), Japanese

Photoemission and Inverse Photoemission Spectroscopy of Trygonal and Amorphous Se.
Ono I., Grekos P., Kouchi T., Ueda T., Tamura M., Matsuda O., Ohba T., Hosokawa S., Namatame H., Taniguchi M., Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 50, 2, 249, 249, 16 Mar. 1995
The Physical Society of Japan (JPS), Japanese

Photoluminescence study on glassy-Ge(S_xSe_<1-x>)_2
Wada Y, Wang Y, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 50, 2, 148, 148, 16 Mar. 1995
The Physical Society of Japan (JPS), Japanese

Temperature dependence of Raman spectra in amorphous, crystalline and liquid GeSe2
Wang Y, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 50, 2, 147, 147, 16 Mar. 1995
The Physical Society of Japan (JPS), Japanese

Laser spot size dependence in photo-induced crystallization process of amorphous GeSe2 film
Nakamura M, Wang Y, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 50, 2, 147, 147, 16 Mar. 1995
The Physical Society of Japan (JPS), Japanese

3a-J-14 Photoluminescence spectra of glassy-and crystalline-GeS_2
Oba T, Wang Y, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1994, 2, 126, 126, 16 Aug. 1994
The Physical Society of Japan (JPS), Japanese

3a-J-13 Photo-induced crystallization of g-GeSe_2 film
Wang Y, Matsuda O, Inoue K, Hashimoto S, Murase K, Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1994, 2, 125, 125, 16 Aug. 1994
The Physical Society of Japan (JPS), Japanese

2a-J-3 Resonance Raman Investigation of K_2Se-doped Crystalline GeSe_2
Kanno H, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1994, 2, 104, 104, 16 Aug. 1994
The Physical Society of Japan (JPS), Japanese

29a-G-11 Raman Investigation of K_2Se-doped crystalline GeSe_2
Kanno H, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 49, 2, 148, 148, 16 Mar. 1994
The Physical Society of Japan (JPS), Japanese

30p-L-5 Photo-induced crystallization in a a-GeSe_2 by modulated light
Oe H, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 49, 2, 171, 171, 16 Mar. 1994
The Physical Society of Japan (JPS), Japanese

30p-L-6 Temperature dependence of photoluminescence of crystalline GeSe_2
Wang Y, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 49, 2, 171, 171, 16 Mar. 1994
The Physical Society of Japan (JPS), Japanese

30p-L-7 Photoluminescence measurements of glassy-GeS_2
Oba T, Wang Y, Matsuda O, Inoue K, Murase K, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 49, 2, 172, 172, 16 Mar. 1994
The Physical Society of Japan (JPS), Japanese

アモルファスGeSe_2の光誘起結晶化と中距離構造(基研短期研究計画「構造不規則系におけるダイナミックス」報告,研究会報告)
邑瀬 和生, 松田 理, 物性研究, 62, 2, 289, 299, 1994
物性研究刊行会, Japanese

12a-DF-12 Raman investigation of laser-annealing process in amorphous Si/SiO^2 multilayer
Matsuda O., Serikawa T., Shirai S., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1993, 2, 157, 157, 20 Sep. 1993
The Physical Society of Japan (JPS), Japanese

12a-DF-18 Photoluminescence of crystal GeSe_2
Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1993, 2, 160, 160, 20 Sep. 1993
The Physical Society of Japan (JPS), Japanese

31p-M-11 Photo-induced crystalization in a-GeSe_2 small structure
Oe H., Matsuda O, Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 48, 2, 163, 163, 16 Mar. 1993
The Physical Society of Japan (JPS), Japanese

31p-M-9 Photoluminescence of Germanium chalcogenide
Wang Y., Matsuda O., Inoue K., Murase K., Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 48, 2, 162, 162, 16 Mar. 1993
The Physical Society of Japan (JPS), Japanese

31p-M-10 Conduction band structure of amorphous GeSe_2 photodoped by Ag and Cu
Nishihara K., Hari Y., Hosokawa S., Taniguchi M., 〓, 〓, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 48, 2, 162, 162, 16 Mar. 1993
The Physical Society of Japan (JPS), Japanese

25a-ZG-15 Raman Investigation of K-doped crystalline GeSe_x(x=1, 2)
Matsumoto T, Matsuda O, Inoue K, Murase K, 秋の分科会講演予稿集, 1992, 2, 113, 113, 14 Sep. 1992
The Physical Society of Japan (JPS), Japanese

30p-X-9 Inverse Photoemission Spectroscopy of a-GeSe_2
Nishihara K., Yokoyama K., Hari Y., miura K., Ueda Y., Taniguchi M., Koyama M., Matsuda O., Murase K., 年会講演予稿集, 47, 2, 200, 200, 12 Mar. 1992
The Physical Society of Japan (JPS), Japanese

27a-F-7 Raman and Photo-Luminescence Investigation of Porous-Si
Matsuda O., Oe H., Nakashima S., Murase K., Inoue K., Maehashi K., Nakashima H., 年会講演予稿集, 47, 2, 229, 229, 12 Mar. 1992
The Physical Society of Japan (JPS), Japanese

30a-W-4 Temperature and excitation energy dependence of photoluminescence in GeSe_2
Nakane T., Matsuda O., Inoue K., Murase K., 年会講演予稿集, 47, 2, 185, 185, 12 Mar. 1992
The Physical Society of Japan (JPS), Japanese

29p-B-8 Raman Investigation of GeSe_2 Small Particles by Gas-evaporation Deposition
Matsuda O., Iwane M., Matsumoto T., Nakane T., Inoue K., Murase K., 年会講演予稿集, 46, 2, 160, 160, 12 Sep. 1991
The Physical Society of Japan (JPS), Japanese

29p-B-9 Temperature dependence of photoluminescence in single-crystalline and amorphous GeSe_2
Nakane T., Matsuda O., Inoue K., Murase K., 年会講演予稿集, 46, 2, 161, 161, 12 Sep. 1991
The Physical Society of Japan (JPS), Japanese

26p-M-5 The Raman investigation of gas-evaporated GeSe_2 fine structures
Nakane T., Matsuda O., Inoue K., Murase K., 春の分科会講演予稿集, 1991, 2, 167, 167, 11 Mar. 1991
The Physical Society of Japan (JPS), Japanese

4a-D-10 Raman spectra of crystalline and amorphous GeSe_2 with model calculations
Inoue K, Matsuda O, Murase K, 秋の分科会講演予稿集, 1990, 2, 156, 156, 12 Sep. 1990
The Physical Society of Japan (JPS), Japanese

4a-D-11 Resonant Raman scattering in micro-crystalline GeSe_2
Matsuda Osamu, Inoue Koichi, Nakane Takayuki, Murase Kazuo, 秋の分科会講演予稿集, 1990, 2, 157, 157, 12 Sep. 1990
The Physical Society of Japan (JPS), Japanese

4a-A-1 Lattics Structures, Vibrational Modes, and Raman Spectra in Germanium Dichalcogenides.
Inoue Koichi, Matsuda Osamu, Murase Kazuo, 秋の分科会講演予稿集, 1989, 2, 207, 207, 12 Sep. 1989
The Physical Society of Japan (JPS), Japanese

4a-A-2 Temperature dependence of Raman spectra in crystalline GeSe_2
Matsuda Osamu, Inoue Koichi, Murase Kazuo, 秋の分科会講演予稿集, 1989, 2, 207, 207, 12 Sep. 1989
The Physical Society of Japan (JPS), Japanese

28p-H-11 Similarity between A-vibration Modes in Amorphous and Crystalline GeSe_2
Murase Kazuo, Inoue Koichi, Matsuda Osamu, 年会講演予稿集, 44, 2, 141, 141, 28 Mar. 1989
The Physical Society of Japan (JPS), Japanese

28p-H-12 Excitation energy dependance of Raman spectra in crystalline GeSe_2
Matsuda Osamu, Inoue Koichi, Okada Hiroshi, Murase Kazuo, 年会講演予稿集, 44, 2, 141, 141, 28 Mar. 1989
The Physical Society of Japan (JPS), Japanese

5a-A2-12 ZnSe-ZnS歪超格子の歪とフォトルミネッセンス
レ ホン・ソン, 井上 恒一, 松田 理, 邑瀬 和生, 秋の分科会講演予稿集, 1988, 2, 151, 151, 16 Sep. 1988
一般社団法人日本物理学会, Japanese

1a-L1-13 ZnSe-ZnS歪超格子のラマン散乱(半導体,(表面・界面・超格子))
レ ホン・ソン, 井上 恒一, 松田 理, 邑瀬 和生, 年会講演予稿集, 43, 2, 119, 119, 31 Mar. 1988
一般社団法人日本物理学会, Japanese

2p-L2-8 アモルファスGeSe2のカラス形成と結晶化過程(半導体,(アモルファス))
井上 恒一, 川本 浩司, 松田 理, 邑瀬 和生, 年会講演予稿集, 43, 2, 167, 167, 31 Mar. 1988
一般社団法人日本物理学会, Japanese

27a-G-14 アモルファスGeSe_2の光誘起結晶化過程
松田 理, 井上 恒一, 川本 浩司, 邑瀬 和生, 秋の分科会講演予稿集, 1987, 2, 124, 124, 16 Sep. 1987
一般社団法人日本物理学会, Japanese

27p-LE-4 アモルファスGeSe_2のレーザー誘起結晶成長速度(半導体)
井上 恒一, 川本 浩司, 邑瀬 和生, 松田 理, 年会講演予稿集, 42, 2, 150, 150, 27 Mar. 1987
一般社団法人日本物理学会, Japanese

30p-A-7 アモルファスGeSe_2のレーザー誘起結晶化
川本 浩司, 井上 恒一, 邑瀬 和生, 松田 理, 秋の分科会講演予稿集, 1986, 2, 262, 262, 12 Sep. 1986
一般社団法人日本物理学会, Japanese

Ultrasonics --- Physics and applications　　　　　　　　　　　　　　　
Osamu Matsuda, Oliver B. Wrigh, Chapter 4 Picosecond laser ultrasonics
IOP publishing, Oct. 2022, 9780750349345, [Contributor]

音響キーワードブック　　　　　　　　　　　　　　　
松田 理, レーザー超音波
コロナ社, 2016, 424-425, Japanese, Scholarly book, [Contributor]

Phononic Crystals: Fundamentals and Applications　　　　　　　　　　　　　　　
Osamu Matsuda, Oliver B. Wright, eds. Abdelkrim Khelif, Ali Adibi, Chap. 7, Optical characterization of phononic crystals in time domain
Springer, 2015, 191-213, English, Scholarly book, [Contributor]

Frontiers in optical methods : nano-characterization and coherent control
Osamu Matsuda, Oliver B. Wright, eds. Ken-ichi Shudo, Ikufumi Katayama, Shin-ya Ohno, Chap. 7, Generation and Observation of GHz--THz Acoustic Waves in Thin Films and Microstructures Using Optical Methods
Springer, 2014, 9783642405938, 129-151, English, Scholarly book, [Contributor]

Current Topics in Amorphous Materials --Science and Technology--　　　　　　　　　　　　　　　
Kazuo Murase, Koichi Inoue, Osamu Matsuda, Medium-range structure and relaxation in chalcogenide glasses investigated by Raman scattering
Elsevier, Amsterdam, 1993, [Joint work]

2次元フォノニック結晶の GHz 音響特性の任意周波数イメージング法を用いた解 析　　　　　　　　　　　　　　　
松田理, 村本裕貴, 古賀裕章, 西田浩紀, 藤田健太郎, 友田基信, ライトオリバー
第80回応用物理学会秋季学術講演会, 18 Sep. 2019, Japanese, Invited oral presentation
20 Sep. 2019 - 21 Sep. 2019, [Invited]

Two-dimensional Imaging of Zero-Group-Velocity Lamb Waves　　　　　　　　　　　　　　　
Oliver B. Wright, Qingnan Xie, Sylvain Mezil, Paul H. Otsuka, Motonobu Tomoda, Jerome Laurent, Zhonghua Chen, Osamu Matsuda
第80回応用物理学会秋季学術講演会, 18 Sep. 2019, English, Invited oral presentation
18 Sep. 2019 - 21 Sep. 2019, [Invited]

Time-resolved imaging of GHz acoustic waves/vibrations in phononic crystals and metamaterials　　　　　　　　　　　　　　　
Osamu Matsuda
METANANO 2019, 16 Jul. 2019, English, Invited oral presentation
15 Jul. 2019 - 19 Jul. 2019, [Invited]

Time-resolved imaging of gigahertz surface acoustic waves: recent development and applications　　　　　　　　　　　　　　　
Osamu Matsuda
Laser Ultrasonics 2018, 10 Jul. 2018, English, Invited oral presentation
09 Jul. 2018 - 13 Jul. 2018, [Invited]

ime-resolved two-dimensional imaging of gigahertz acoustic waves in phononic crystals and related structures　　　　　　　　　　　　　　　
Osamu Matsuda
Photonics West 2018, 01 Feb. 2018, English, Invited oral presentation
28 Jan. 2018 - 01 Feb. 2018, [Invited]

Time-domain Brillouin scattering assisted by diffraction gratings　　　　　　　　　　　　　　　
O. Matsuda, T. Pezeril, I. Chaban, K. Fujita, V. E. Gusev
2017 International Congress on Ultrasonics, 19 Dec. 2017, English, Invited oral presentation
18 Dec. 2017 - 20 Dec. 2017, [Invited]

Ultrafast imaging of acoustic wave propagation in microsphere-based metamaterial structures　　　　　　　　　　　　　　　
P. H. Otsuka, S. Mezil, V. Gusev, O. Matsuda, M. Tomoda, T. Gan, N. Boechler, A. A. Maznev, N. Fang, O. B. Wright
The 8th International Conference on Metamaterials, Photonic Crystals, and Plasmonics (META '17), 25 Jul. 2017, English, Invited oral presentation
25 Jul. 2017 - 28 Jul. 2017, [Invited]

Optical detection of picosecond acoustic waves generated in grating structures　　　　　　　　　　　　　　　
Osamu Matsuda, Thomas, Pezeril, Ievgeniia Chaban, Vitalyi Gusev
19th International Conference on Photoacoustic and Photothermal Phenomena (ICPPP19), 18 Jul. 2017, English, Invited oral presentation
16 Jul. 2017 - 20 Jul. 2017, [Invited]

Time-resolved Imaging of Surface Acoustic Waves Propagating in Two-dimensional Phononic Crystals　　　　　　　　　　　　　　　
Osamu Matsuda, Hiroki Nishita, Hiroaki Koga, Paul H. Otsuka, Motonobu Tomoda, Oliver B. Wright
the 4th international conference on phononic crystals/metamaterials, phonon transport/coupling and topological phononics, 09 Jun. 2017, English, Invited oral presentation
04 Jun. 2017 - 09 Jun. 2017, [Invited]

Mapping surface phonons in phononic crystals in real- and k-space　　　　　　　　　　　　　　　
Paul Otsuka, Ryota Chinbe, Motonobu Tomoda, Osamu Matsuda, Oliver B. Wright, Istvan Veres, Joo-Hyung Lee, Jun-Bo Yoon
Phononics 2013, 03 Jun. 2013, English, Invited oral presentation
02 Jun. 2013 - 06 Jun. 2013, [Invited]

Time-resolved imaging of the negative refraction of GHz surface acoustic waves in phononic crystals　　　　　　　　　　　　　　　
O. Matsuda, Hiroaki Koga, Motonobu Tomoda, Ryota Chinbe, Hirotaka Sakuma, Paul, H. Otsuka, Istvan A. Veres, Oliver B. Wright
Phononics 2013, 03 Jun. 2013, English, Invited oral presentation
02 Jun. 2013 - 06 Jun. 2013, [Invited]

Picosecond laser ultrasonics in GaAs/AlGaAs quantum wells containing spin-polarized excited carriers　　　　　　　　　　　　　　　
O. Matsuda, C. Li, R. Harley, O. B. Wright, P. Lagoudakis
International Congress on Ultrasonics -- ICU 2013, 03 May 2013, English, Invited oral presentation
02 May 2013 - 05 May 2013, [Invited]

Time-resolved two-dimensional imaging of GHz surface acoustic waves in phononic crystals and structures based on them　　　　　　　　　　　　　　　
O. Matsuda
International School of Quantum Electronics, Second Mediterranean International Workshop on Photoacoustic & Photothermal Phenomena: Focus on Biomedical and Nanoscale Imaging and NDE, 24 Apr. 2012, English, Invited oral presentation
19 Apr. 2012 - 26 Apr. 2012, [Invited]

Picosecond laser ultrasonics in materials physics　　　　　　　　　　　　　　　
O. Matsuda
International School of Quantum Electronics, Second Mediterranean International Workshop on Photoacoustic & Photothermal Phenomena: Focus on Biomedical and Nanoscale Imaging and NDE, 20 Apr. 2012, English, Invited oral presentation
19 Apr. 2012 - 26 Apr. 2012, [Invited]

Dynamic imaging of surface acoustic waves in phononic crystals　　　　　　　　　　　　　　　
Oliver B. Wright, Istvan A. Veres, Dieter M. Profunser, Osamu Matsuda, Brian Culshaw, Udo Lang
SPIE Smart Nano+Micro Materials and Devices, 07 Dec. 2011, English, Invited oral presentation
05 Dec. 2011 - 07 Dec. 2011, [Invited]

Imaging gigahertz vibrations trapped in phononic crystal cavities　　　　　　　　　　　　　　　
Oliver Wright, Ryota Chinbe, Paul H. Otsuka, Motonobu Tomoda, Osamu Matsuda, Yukihiro Tanaka
16th International Conference on Photoacoustic and Photothermal Phenomena, 27 Nov. 2011, English, Invited oral presentation
[Invited], [International presentation]

Dynamic imaging of gigahertz phonons on phononic crystal slabs　　　　　　　　　　　　　　　
O. B. Wright, R. Chinbe, P. H. Otsuka, M. Tomoda, O. Matsuda, Y. Tanaka, I. A. Veres, S. Kim, H. Jeon
Phononics 2011, 30 May 2011, English, Invited oral presentation
29 May 2011 - 02 Jun. 2011, [Invited], [International presentation]

Time-resolved two-dimensional imaging of GHz surface acoustic waves in 1D and 2D phononic crystals and devices based on them　　　　　　　　　　　　　　　
Osamu Matsuda, Istvan A. Veres, Oliver B. Wright
Photonics West 2011, 22 Jan. 2011, English, Invited oral presentation
[Invited], [International presentation]

Measurement of surface displacement in picosecond laser acoustics free from the photoelastic effec　　　　　　　　　　　　　　　
O. Matsuda, K. Aoki, T. Tachizaki, O. B. Wright
International Congress on Ultrasonics -- ICU 2009, 11 Jan. 2009, English, Invited oral presentation
[Invited], [International presentation]

Surface acoustic waves propagating on microstructured phononic crystals　　　　　　　　　　　　　　　
D. Profunser, O. Wright, O. Matsuda, Y. Tanaka, A. Khelif, V. Laude, S. Benchabane
Acoustics '08, 29 Jun. 2008, English, Invited oral presentation
[Invited], [International presentation]

Measurement of the velocity dispersion and attenuation in a liquid metal at GHz frequencies　　　　　　　　　　　　　　　
O. Wright, B. Perrin, O. Matsuda, V. Gusev
Acoustics '08, 29 Jun. 2008, English, Invited oral presentation
[Invited], [International presentation]

Stroboscopic interferometric full-field imaging of laser-induced surface acoustic waves　　　　　　　　　　　　　　　
B. Sarens, O. Matsuda, X. Xu, G. Kalogiannakis, R. Salenbien, R. Cote, C. Glorieux
Acoustics '08, 29 Jun. 2008, English, Invited oral presentation
[Invited], [International presentation]

Optical detection of longitudinal and shear acoustic waves with laser picosecond acoustics　　　　　　　　　　　　　　　
O. Matsuda, O. B. Wright, D. H. Hurley, V. Gusev, K. Shimizu
Acoustics '08, 29 Jun. 2008, English, Invited oral presentation
[Invited], [International presentation]

Visualizing high-frequency surface acoustic waves propagating in microstructured phononic metamaterials　　　　　　　　　　　　　　　
Dieter M. Profunser, Oliver B. Wright, Osamu Matsuda, Udo Lang, Abdelkrim Khelif, Sarah Benchabane, Vincent Laude
International Congress on Ultrasonics, 09 Apr. 2007, English, Invited oral presentation
[Invited], [International presentation]

Inversion techniques applied to picosecond acoustics　　　　　　　　　　　　　　　
M. Tomoda, R. Li Voti, O. Matsuda, O. B. Wright
Thermo International 2006, 30 Jul. 2006, English, Invited oral presentation
[Invited], [International presentation]

Internal friction and dispersion at GHz frequencies in liquid mercury　　　　　　　　　　　　　　　
O. B. Wright, B. Perrin, O. Matsuda, V. E. Gusev
The 14th International Conference on Internal Friction and Mechanical Spectroscopy, 05 Sep. 2005, English, Invited oral presentation
[Invited], [International presentation]

Picosecond acoustic phonon pulses generated and detected with ultrashort optical pulses　　　　　　　　　　　　　　　
Osamu Matsuda
Japanese Physical Society Meeting, Sep. 2005, Japanese, Invited oral presentation
[Invited], [Domestic Conference]

Generation and detection of picosecond shear acoustic pulses with ultrashort laser pulses in anisotropic materials　　　　　　　　　　　　　　　
Osamu Matsuda, Oliver Wright, David Hurley, V. E. Gusev, K. Shimizu
World Congress on Ultrasonics - Ultrasonics International 2005, 29 Aug. 2005, English, Invited oral presentation
[Invited], [International presentation]

Picosecond acoustics in semiconductor quantum wells　　　　　　　　　　　　　　　
O. Matsuda, T. Tachizaki, T. Fukui, J. J. Baumberg, O. B. Wright
Photonics West 2005, 22 Jan. 2005, English, Invited oral presentation
[Invited], [International presentation]

Measurement of dispersion relations of point-excited surface acoustic waves　　　　　　　　　　　　　　　
O. B. Wright, O. Matsuda, Y. Sugawara
Ultrasonics International 2003, 30 Jun. 2003, English, Invited oral presentation
[Invited], [International presentation]

Picosecond acoustics in quantum wells　　　　　　　　　　　　　　　
O. Matsuda
Gordon Research Conference on Photoacoustic & Photothermal Phenomena 2003, 08 Jun. 2003, English, Invited oral presentation
[Invited], [International presentation]

Real time imaging of surface acoustic waves in thin films and microstructures　　　　　　　　　　　　　　　
O. B. Wright, Y. Sugawara, O. Matsuda, V. E. Gusev
12th International conference on Photoacoustic and Photothermal Phenomena, 23 Jun. 2002, English, Invited oral presentation
[Invited], [International presentation]

Real time imaging of surface acoustic waves on opaque substrates　　　　　　　　　　　　　　　
O. B. Wright, Y. Sugawara, O. Matsuda
Autumn Meeting of the Acoustical Society of Japan, 2002, English, Invited oral presentation
[Invited], [Domestic Conference]

Ripples on crystals　　　　　　　　　　　　　　　
O. B. Wright, Y. Sugawara, O. Matsuda
2nd Phonon Engineering Forum, 2002, English, Invited oral presentation
[Invited], [International presentation]

Real time imaging and dispersion of surface phonons　　　　　　　　　　　　　　　
Oliver B. Wright, Yoshihiro Sugawara, Vitalyi E. Gusev, Osamu Matsuda
Phonons 2001, 12 Aug. 2001, English, Invited oral presentation
[Invited], [International presentation]

Spatiotemporal mapping of surface acoustic waves in isotropic and anisotropic materials　　　　　　　　　　　　　　　
Yoshihiro Sugawara, Oliver B. Wright, Osamu Matsuda, Vitalyi E. Gusev
Ultrasonics International 2001, 02 Jul. 2001, English, Invited oral presentation
[Invited], [International presentation]

Study of new transduction mechanisms for laser picosecond acoustics　　　　　　　　　　　　　　　
David H. Hurley, Oliver B. Wright, Osamu Matsuda, Vitalyi E. Gusev, Oleg. V. Kolosov, K. Sueoka, K. Mukasa, A. Subagyo
Ultrasonics International / World Congress on Ultrasound, 29 Jun. 1999, English, Invited oral presentation
[Invited], [International presentation]

応用物理学　　　　　　　　　　　　　　　
北海道大学

電子系物理工学特論　　　　　　　　　　　　　　　
北海道大学大学院

力学演習　　　　　　　　　　　　　　　
北海道大学

電磁気学II　　　　　　　　　　　　　　　
北海道大学

応用数学I　　　　　　　　　　　　　　　
北海道大学

力学　　　　　　　　　　　　　　　
北海道大学

応用物理学実験法　　　　　　　　　　　　　　　
北海道大学

光物理学I　　　　　　　　　　　　　　　
北海道大学

先端系物性工学特論　　　　　　　　　　　　　　　
北海道大学大学院

現代物理学概論　　　　　　　　　　　　　　　
北海道大学

物理学I　　　　　　　　　　　　　　　
北海道大学

Development of Ultrasonic Topological Phononics for Multifunctional Elastic Wave Devices
Grants-in-Aid for Scientific Research
05 Jul. 2021 - 31 Mar. 2026
鶴田 健二, 竹澤 晃弘, 松田 理, 畑中 大樹, O・B Wright
本研究では，計算科学的バンド設計に基づいてトポロジーで保護されたエッジモードの発現を予測，力学系にモデル化・可視化，その知見からエッジモードを介した極めて低損失な音波・弾性波伝搬実現を目指している。初年度は各班で以下の取組・成果が得られた。
【(岡大+早大)班】 これまでに設計したC3v対称性を持つ水中2次元フォノニック構造を薄膜系に拡張し，kHz～MHz帯でエッジモードが発現するフォノニック構造を設計した。並行して，既知構造をベースに，位相最適化法を用いてより高いロバスト性を持つ最適構造探索に成功，また，それらのプロトタイプ構造を３Dプリンタで試作し，レーザードップラー計測を行った。一方，GHz帯の設計構造は北大班ならびにNTT班で試作・評価を実施中である。
【北大班】 すでに着手しているフォノニック構造中を伝搬する表面弾性波の時間分解計測による可視化については，強誘電体基板上の銅ピラー構造によるフォノニック結晶で分散関係取得のための予備的な測定を行った。マクロスコピックなメカニカルフォノニック結晶におけるトポロジカルエッジモードの可視化については，回転可能なメカニカルグラフェン構造を設計・製作し，モーションキャプチャーシステムによる同構造の振動測定と解析を進めている。
【NTT班】(岡大+早大)班がGHz帯で設計したトポロジカルフォノニック導波路構造をMEMS作製技術の援用により試作し，エッジモード励起も確認した。並行して，磁性体装荷のGHzフォノニック結晶素子を作製し，強磁性マグノンによる共振周波数とQ値の変化を確認した。同時に，有限要素法を用いた数値解析法を構築し，計算による当該素子構造における磁気弾性変調効果のシミュレーションを行った。
また，代表者・分担者・協力研究者による「トポロジカルフォノニクス研究会」を年度内に４回オンライン開催し多数の参加者を得ている。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (S), Okayama University, 21H05020

Optical generation and detection of GHz-THz acoustic waves in 1- and 2-dimensional nano-scale periodic structures and their application
Grants-in-Aid for Scientific Research
01 Apr. 2022 - 31 Mar. 2025
松田 理, 友田 基信
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 22K04938

Experiments, theories, and applications of space-time-dependent metamaterials that allow visualization of wave phenomena
Grants-in-Aid for Scientific Research
01 Apr. 2022 - 31 Mar. 2025
友田 基信, 松田 理
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 22H01930

Development and quantitative interpretation of acoustic and phoxonic metamaterial devices from kHz to GHz frequencies
Grants-in-Aid for Scientific Research
26 Jun. 2019 - 31 Mar. 2022
Wright Oliver
We propose the development and quantitative interpretation of acoustic and phoxonic metamaterial devices from kHz to GHz frequencies, opening new frontiers in metamaterials. We will generate acoustic waves with frequencies ~0.1 kHz-1 GHz and wavelengths from the millimeter scale down to micro- and nano-scales to control bulk, rod, plate and flexural acoustic waves in both fluid and solid metamaterials, as well as developing the new field of phoxonic, i.e. simultaneous photonic and phononic, metamaterials with the aim to create practical devices. We will investigate metamaterial-based acoustic microscopy, metasurfaces for air-water transmission, lightweight single-component metapillars, metaplates or meta-atoms for wideband multimode acoustic isolation or sub-diffraction limit focusing, as well as the creation of phoxonic metamaterials.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (S), Hokkaido University, 19H05619

Time-resolved imaging of GHz surface acoustic waves and controlling acoustic chirality
Grants-in-Aid for Scientific Research
01 Apr. 2017 - 31 Mar. 2020
Matsuda Osamu
In this project, we have established the experimental method to achieve the time-resolved two-dimensional imaging of GHz surface acoustic waves at arbitrary frequencies. The technique overcomes the restriction of the existing techniques, i.e. the insufficient frequency resolution. The technique can be utilized to the development of materials and devices which exploit surface acoustic waves. We have used the developed technique to study the properties of the phononic band gaps of phononic metamaterials, of the zero group velocity modes of Lamb waves on a plate, etc. We also have established the way to control the chirality of the acoustic field. As a related study, we have designed and fabricated a metamaterial rod structure which shows the perfect band gap, i.e. the band gap for all the possible acoustic modes at certain frequency range.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 17H02807

GHz laser-ultrasonic computed tomography
Grants-in-Aid for Scientific Research
01 Apr. 2016 - 31 Mar. 2019
Wright Oliver, Otsuka Paul H., Mezil Sylvain, Devaux Theabaut, Gusev Vitalyi E., Voti Roberto Li, Juodkazis Saulius, Maznev Alex A., Dehoux Thomas, Lee Sam H.
This research concerns GHz ultrasonic computed tomography, which extends the field of non-invasive acoustic internal imaging to the nanoscale. We make use of the optical generation of coherent phonons with frequencies up to ~100 GHz and wavelengths down to ~50 nm in nanostructures to image bulk acoustic waves on very small temporal (~1 ps) and spatial (~50-500 nm) scales. Elastic property imaging, nanoscale acoustic-optic interactions and defect phonon scattering are investigated. This work should lead to new sensing and imaging technologies.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 16H02123

Implementation of GHz plate phononic metamtaterials and plasmonic phononic crsytals
Grants-in-Aid for Scientific Research
01 Apr. 2016 - 31 Mar. 2019
Tomoda Motonobu, Otsuka Paul H., Mezil Sylvain, MINAMIMOTO Hiro, NOMURA Masahiro, Gusev Vitalyi E., Balogun Olwaseyi
We controled GHz elastic waves propagating on plates with nanoscale thickness using artificial phononic structures as follows. We designed double negative flexural wave metamaterials and simulated negative refractions. We designed a plasmonic phononic crsytal with perfect phononic bandgap. We imaged surface acoustic waves on a microsphere-based elastic metamaterial structure. We measured reflectivity change on split ring resonators due to mechanical vibrations.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 16H03997

Time-resolved imaging of GHz surface acoustic waves using two-dimensional imaging devices
Grants-in-Aid for Scientific Research
01 Apr. 2016 - 31 Mar. 2018
Matsuda Osamu, PEZERIL Thomas, FUJITA Kentaro
To achieve the fast time-resolved two-dimensional imaging of GHz surface acoustic waves using two dimensional imaging device, we performed the following studies. 1) The interferometer optics which transfers images of surface displacement caused by the acoustic vibration to the imaging plane of the camera as the intensity images has been prototyped, and its functionality has been confirmed. 2) Self-adopted interferometer setup using photo-refractive crystal has been considered. 3) The software for the fast transfer and analysis of images for high-speed CCD camera has been developed. As the secondary studies, 4) the light scattering theory for the quantitative handling of the modulation of the light reflection by the acoustic waves has been developed, and 5) the optical generation of detection of acoustic waves using nano-scale metal grating structure has been studied.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 16K13713

Construction and application of GHz acoustic metamaterials
Grants-in-Aid for Scientific Research
21 Oct. 2013 - 31 Mar. 2016
Wright Oliver, MATSUDA Osamu, TOMODA Motonobu, Otsuka Paul, Mezil Sylvain, Gusev Vitali, Lee Sam Hyeon, Kuipers L. Kobus
We investigate gigahertz acoustic metamaterials, extending them to the nanoscale and thus facilitating the development of new nanoscale acoustic microscopies. The aim is to optically generate coherent phonons with frequencies ~1-100 GHz and wavelengths down to ~100 nm in nano-metamaterials to control bulk and surface acoustic waves on very short temporal (~1 ps) and spatial (~20-50 nm) scales. Applications include solid-state super-lensing, extraordinary transmission, negative refraction, surface acoustic wave cloaking, metamaterial resonators and hybrid opto-mechanical materials. We concentrate on three main topics: 1. Design of GHz acoustic metamaterials, 2. GHz extraordinary transmission, metamaterial resonators, and deep-sub-wavelength focusing, 3. Hybrid GHz opto-mechanical metamaterials. During the course of this work a number of supplementary applications were conceived at lower frequencies.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 25246030

Development of laser picosecond ultrasonic microscopy with micro ultrasonic lens
Grants-in-Aid for Scientific Research
01 Apr. 2013 - 31 Mar. 2016
Tomoda Motonobu, WRIGHT Oliver B., MATSUDA Osamu, Otsuka Paul, Mezil Sylvain, Juodkazis Saulius, Ulbricht Ronald, Gusev Vitali
We developed ultrasonic microscopy techniques with high frequencies and high resolutions, aiming to measure and image surface topographies and three-dimensional internal structures of samples. This technique is based on laser picosecond ultrasonics which generate and detect ultrasonic pulses at 10-100 GHz.
We did ultrasonic focusing with micro-structures like a micro-ultrasonic-lens and a micro-fiber, making a smaller probe light spot by use of a high numerical aperture oil-immersion objective lens, high resolution depth-profile ultrasonic measurements in transparent samples, development of arbitrary frequency measurements which are not restricted to repetition pulse laser frequencies, and controlling of pump beam spot shapes.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 25390114

Ultrafast phononic plasmonics
Grants-in-Aid for Scientific Research
2010 - 2012
OLIVER B. Wright, MATSUDA Osamu, TOMODA Motonobu, OTSUKA Paul, JEREMY Baumberg, L. KOBUS Kuipers
By means of an ultrafast optical technique, we investigate the coupling of high frequency phonons at GHz frequencies with metallic plasmonic structures. Various samples are probed, including nanovoid arrays, lattices of tiny holes exhibiting extraordinary optical transmission (EOT) and nanoscale linear waveguides. For the nanovoid arrays, we reveal GHz breathing vibrations of the voids by 2D imaging, showing how the vibrations couple to localized Mie plasmons. For the EOT samples, we reveal collective vibration of the hole arrays, and their effect on the optical transmission modulation. For the waveguides we describe work in progress, and fabrication of nanoscale linear gold waveguides.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, Coinvestigator not use grants, Competitive research funding, 22246012

Controlling electronic and optical properties in semiconductor quantum structures using surface acoustic waves
Grants-in-Aid for Scientific Research
2008 - 2011
MATSUDA Osamu, WRIGHT Oliver, TOMODA Motonobu
We aimed to transfer the excitons and to control their life time in semiconductor samples using the surface acoustic waves generated by the ultrashort light pulse absorption. For this purpose, we developed an experimental technique which allows the time resolved two-dimensional imaging of the GHz surface acoustic wave propagation and the two-dimensional imaging of the photoluminescence at the same region of the sample at low temperature (10K). Connecting to this, we also developed a heterodyne technique which use the modulated light for both excitation and probing light. We also developed an analyzing method for the strain components using the polarization of the probing light.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, Principal investigator, Competitive research funding, 20360038

Visualization and Mode-Control of Phonons Confined in Microstructures
Grants-in-Aid for Scientific Research
2007 - 2009
O・B Wright
This work involves the imaging and control of phonon modes confined in a wide variety of novel microscopic geometries with unprecedented picosecond temporal, micron spatial, and megahertz frequency resolutions. The following topics are investigated : visualizing Bloch waves and modes in phononic crystals, phononic crystal waveguides and cavities, investigating whispering gallery modes, acoustic negative refraction, and phase singularities in surface acoustic wave fields, and applications to industrially-produced surface acoustic wave resonators. Visualization and Mode-Control of Phonons Confined in Microstructures
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, Coinvestigator not use grants, Competitive research funding, 19206013

Generation and detection of picosecond shear acoustic pulses by ultra short light pulses and their application to materials physic
Grants-in-Aid for Scientific Research
2005 - 2007
MATSUDA Osamu, WRIGHT B. Oliver, TOMODA Motonobu
Picosecond acoustic pulses can be used to study the internal structure of medium in nanometer spatial region, or the electron and lattice dynamics of medium in picosecond temporal region. Especially a method named picosecond laser ultrasonics, which uses ultra short light pulses for the generation and detection of the acoustic pulses, has been exploited to evaluate the thickness profile and elastic properties of multilayers, or to study the ultrafast dynamics of photo-induced carriers. In the previous studies, mostly the longitudinal acoustic waves have been used because of the symmetry of the system. However, the additional usage of shear acoustic waves would be favorable to extend the applicability of the method. This research aims to develop the picosecond laser ultrasonics using shear acoustic waves and to apply the method to various studies in materials physics.
The main achievements are as follows. 1) With the low symmetry surface of the anisotropic medium such as Zn and GaAs single crystals, the laser picosecond ultrasonics measurement is carried out. We develop a general light scattering theory for the inhomogeneously modulated multilayers of anisotropic medium. With this theory, the experimental results were quantitatively analyzed to retrieve the photoelastic tensor components, ultrasonic absorption coefficients, electron-phonon interaction coefficients, etc.. 2) We develop a method for the picosecond laser ultrasonics measurement in liquids. The acoustic pulses are generated at the GaAs single crystal and their propagation in water and glycerol is studied. 3) We develop a method to measure the surface displacement caused by the acoustic waves independent of the photoelastic signal. 4) We develop a theory for the acoustic wave propagation in inhomogeneous medium. 5) We develop a method to map the elastic properties of polycrystalline medium with the anisotropic acoustic wave propagation. The method is utilized to study the Cu polycrystals and the artificial phononic crystals.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, Principal investigator, Competitive research funding, 17360024

フォトニック結晶ファイバーによる超高速音響光学変調器の開発
科学研究費助成事業
2004 - 2005
WRIGHT O・B, 松田 理, 友田 基信, 田村 信一朗
我々は、ローマ大学「ラ・サピエンザ」のR.Li Voti博士から提供された高精度のTiO_2/Ag多層膜試料を用い、試料中を伝播するピコ秒超音波の広範囲にわたる波長依存性・時間分解の測定を行った。同期した2つの波長可変な超短パルスレーザーシステムを使い、反射率変化の応答を観測した。この試料はフォトニックバンドギャップを波長400nm以下と800nm以上の光に対してもつので、ポンプ光の波長を800nmに固定してプローブ光の波長を400nm付近のバンドギャップエッジの周りで変化させ測定を行った。
プローブ光の波長を400nmから長波長側へ走査し、プローブ光の波長により試料の反射率変化が増大することを発見した。これは、1次元フォトニック構造においてフォトニックバンドギャップが超高速音響光学作用を増大することに利用できることを結論付けるものである。
我々はまた、プローブ光が試料中で多重反射する効果も含めた転送行列法によって、試料中を伝播するピコ秒超音波による反射率変化についての数値的なシミュレーションを行った。この理論結果は、すべてのプローブ光の波長領域において実験結果と一致し、これは初めてフォトニック構造におけるピコ秒時間領域での音響光学変調を定量的に評価したことになる。
この研究は、さらに2次元や3次元フォトニック結晶におけるピコ秒音響光学作用に研究を拡張する基礎となるものである。
日本学術振興会, 萌芽研究, 北海道大学, Coinvestigator not use grants, Competitive research funding, 16656020

Spatial visualization of electron wavefunctions and acoustic phonon transduction in semiconductor quantum wells and related applications
Grants-in-Aid for Scientific Research
2001 - 2005
WRIGHT Oliver B., MATSUDA Osamu, TOMODA Motonobu
1)THz phonon generation and detection experiments were done on 2-well and 3-well GaAs/GaAlAs samples with surface-absorbed probe optical pulses and wavelength-tuned pump optical pulses. These first spectroscopic experiments in the domain of picosecond acoustics (up to 0.3 THz) were successfully treated with theoretical models to describe the phonon generation and detection in these multilayers. We also characterized the spectral generation efficiency.
2)Improvements in temporal and spatial resolution were achieved using shorter (〜400 fs) optical pulses to demonstrate detection at frequencies up to 0.5 THz. We also developed a new optical-polarization-sensitive oblique-incidence technique, tested on Cr, to separate different signal contributions, and modelled the phonon pulse shapes for this sample.
3)A Novel ultrafast Sagnac interferometer was developed for picosecond phonon detection with 1 μm spatial resolution, applicable to semiconductors, involving a single focusing objective.
4)Bulk GaAs picosecond acoustics was implemented to help interpret the quantum well results, we investigated ultrafast phonon generation in 3 different GaAs samples. We demonstrate the generation of picosecond shear pulses using anisotropic cuts and pulse-broadening by electron diffusion.
5)A novel detection scheme based photoluminescence was extensively tested on quantum well samples. The results show that we require a higher detection sensitivity to achieve detection of phonon -pulses detection within a quantum well rather than at the surface.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (S), HOKKAIDO UNIVERSITY, Coinvestigator not use grants, Competitive research funding, 13852006

Two-dimensional real time imaging of the propagation of surface waves on materials in picosecond temporal regime
Grants-in-Aid for Scientific Research
2002 - 2003
MATSUDA Osamu, TOMODA Motonobu, TAMURA Shin-ichiro, WRIGHT B. Oliver
Imaging of the surface acoustic phonon focusing phenomena reveals complicated patterns of the acoustic energy propagation in anisotropic materials. The imaging technique is expected to play an important role in the development of surface acoustic wave devices in GHz frequency region. In this study, we develop a real-time two-dimensional imaging technique for the surface acoustic wave propagation. It is based on the ultrafast optical pump-probe method and the extremely stable common-path optical interferometer. In case of the diamond substrate covered with Au film, it is shown that the surface acoustic phonon up to 2 GHz is generated and detected by this method. We also develop the analysis method to obtain the multiple mode of the surface acoustic phonon directly from the experimental results on transparent and opaque, isotropic and anisotropic samples.
As a new imaging technique especially for opaque samples, a method using automated mirror is developed. As for the detection of the surface acoustic wave, instead of the interferometer, the method based on the reflectivity change is developed. In relation to this, we develop the light scattering theory that is applicable to the normal and non-normal probe light incidence to the anistropic multilayer sample with inhomogeneous optical properties.
As an application of the technique, the surface acoustic wave is imaged in the poly-crystalline Cu sample consists of micron size grains. The diffraction and reflection at the grain boundary is clearly observed. The result is compared with the simulation based on the FDTD method. It provides the opportunity to evaluate the subsurface structure around the grain boundaries.
In summary, we have developed the general purpose surface acoustic wave measurement and analysis method with pico-second time resolution and micron scale spatial resolutions. By this method, we have clarified the physics of surface acoustic wave propagation in MHz-GHz frequency region.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, Principal investigator, Competitive research funding, 14205014

Nanometer scale real-time mapping of vibrations in pico second tempral region
Grants-in-Aid for Scientific Research
2000 - 2001
MATSUDA Osamu, INAGAKI Katsuhiko, MUTO Shunichi, WRIGHT B. Oliver
In this research, we aim to develop a new microscope which has both nanometer spatial resolution and picosecond temporal resolution. It can be realized by the combination of the scanning probe microscope and the time-resolved measurement technique with ultrashort laser pulses. The former has the nanometer spatial resolution and the latter the picosecond temporal resolution. The combination of the ultra high speed optical switch with ultra short laser pulses and the scanning tunneling microscope has been already proposed along this way. It is proved, however, that the stray capacity between the sample and the microscope tip substantially reduces the spatial resolution when the tunnel current is switched very fast. As a way getting around the above problem, we propose a scanning probe microscope that detects ultrashort phonon pulses excited by ultrashort laser pulses.
The ultrashort light pulses from a mode-locked Ti-sapphire laser are divided into two optical paths. An optical delay line is used to introduce a time difference of ± 1 ns between the pulses in two paths. The pulses passing each line are modulated with different frequencies. A metal thin film sample is irradiated by the modulated light pulses to generate the ultrashort acoustic phonon pulses. The generated periodic surface displacement is detected by the atomic force microscopy. We considered this method theoretically and did actual experiments. In addition, we did related studies of the technique to estimate the local elasticity with nanometer spatial resolution by the ultrasonic force microscope and of the ultra high frequency phonon generation by a semiconductor quantum well structure.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, Principal investigator, Competitive research funding, 12305007

光ヘテロダイン原子間力顕微鏡による固体熱物性のナノスケールイメージングの研究
科学研究費助成事業
2000 - 2001
WRIGHT Oliver B., 松田 理
本研究は、固体熱物性の空間的分布をナノスケールで画像化できる光学ヘテロダイン原子間力顕微鏡を開発することを目的とした。試料表面においてレーザー照射により光熱的に励起された超音波振動(周波数100MHz以下)の振幅および位相を、ナノメートルの横空間分解能で2次元画像化する。これにより試料表面および表面下の熱的な性質についてのナノメートル空間分解能測定を可能にする。
以下に示すようにして光ヘテロダイン原子間力顕微鏡を構築した。SiN透明カンチレバーを持つ原子間力顕微鏡のカンチレバー支持部に圧電素子をとりつけ、カンチレバーを周波数ω_1=11MHzにて振動させる。探針による試料表面の観察部位にω_1近傍の周波数ω_2で変調された赤外光を照射し試料表面に周期的な熱振動を励起する。試料表面は試料の局所的熱物性を反映してω_2による膨張収縮を繰り返す。試料探針間相互作用の試料探針間距離に対する非線形性により、カンチレバーの平均変位はω_1-ω_2の振動数で変化する。この変化の振幅と位相を原子間力顕微鏡の光てこ検出部を用いて検出し画像化する。試料としてSi基板上にCr薄膜(膜厚100nm)およびSiO_2/Cr薄膜(膜厚150nm/100nm)を作製したものを用いた。これらは同一基板上にμmスケールのモザイク状に形成されている。試料表面層は同一膜厚のCr層で覆われているので、表面から100nm深さまでの機械的な性質は試料表面の場所によらないようになっている。この試料についての光ヘテロダイン顕微鏡による観測を行った。試料表面下のSiO_2層の有無による熱物性の違いを反映して、位相像に大きなコントラストが得られた。1次元熱拡散モデルに基づいてこのコントラストを半定量的に解析した。これらの結果により光ヘテロダイン顕微鏡が試料表面下の局所的熱物性を画像化する有力な手段であることが示された。
日本学術振興会, 萌芽的研究, 北海道大学, Coinvestigator not use grants, Competitive research funding, 12875007

Evaluation of local elasticity and inelasticity with nonoscale spatial resolution with scanning ultrasonic force microscope
Grants-in-Aid for Scientific Research
1999 - 2000
MATSUDA Osamu, INAGAKI Katsuhiko, MUTO Shunichi, WRIGHT Oliver,b, YAMAMOTO Noritaka
In this research, we develop the scanning ultrasonic probe microscope with lateral resolution < 1 nm and study the physics involved in it. The contributions of elasticity, viscosity, surface energy at the sample-tip interface to the sample and cantilever dynamics are analyzed distinctively in order to carry out the quantitative measurement on the surface and subsurface local complex elasticity.
A commercial AFM is modified by attaching the PZT transducer at the cantilever base or on the scanner to make the scanning ultrasonic probe microscopy which is capable to apply the ultrasonic vibration to the cantilever or the sample. At various frequency below and above the cantilever resonance frequency and at various ultrasonic amplitude, we carry out the force curve measurement on Si and GaAs single crystals. The vibration amplitude is calibrated with Michelson enterferomenter. The obtained force curve has the following common features : 1)In case of no applied vibration, small "jump-in" in the approach phase and large "jump-out" in the retraction phase are observed. 2)Within creasing the vibration amplitude, the "jump-out" position rapidly approaches to the "jump-in" position. 3)At above certain vibration amplitude, a new "repulsive jump' is observed for both approach and retraction phase.
These results are analyzed by considering the cantilever motion numerically with the finite difference method. In the analysis, we give the elasticity of the tip and sample, damping, adhesion, and assume the JKR model for the tip-sample interaction. The result explains the features 1)and 2)quantitively and proves the validity of the analysis.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B)., Hokkaido University, Principal investigator, Competitive research funding, 11555018

Nanoscale Probing of Ultrafast Coherent Phonon Generation and Electron Diffusion in Metals
Grants-in-Aid for Scientific Research
1999 - 2000
WRIGHT Oliver b., MATSUDA Osamu, TAMURA Shinichiro
In main aim of this study is to extend our knowledge of ultrafast acoustic phonon generation using femtosecond light pulses to basic metallic materials and nanostructures. The phonon pulse propagation dynamics in such materials and the phonon generation mechanisms can be studied. The use here of a tightly focused excitation and probe light beams a few microns in diameter allow the detection of phonons with -10 μm spatial resolution. In order to do this we have made use of an ultrafast reflectometry and interferometry for measurements at normal incidence.
We have carried out the first generation and detection of coherent phonons in amorphous and liquid metals. The results for Hg demonstrate that electron diffusion is very likely to be influencing the phonon generation. An interesting asymmetric pulse shape was observed. The first demonstration that picosecond phonon pulses could be generated and detected in an amorphous metal was also successful.
Coherent phonon generation and detection experiments in transition metals with -100 fs optical pulses, in particular for Cr and for Ni, shows that we can successfully model the phonon pulse shapes with the two-temperature model, taking due account of ultrasonic attenuation measured in experiment.
Ultrashort optical pulse experiments in transition metals with -10 fs optical pulses have been attempted for the first time. Using a -20 fs order optical pulse width in the infrared for both the pump and probe beams, the effect of ultrafast electron diffusion on ultrashort timescales is clearly evident in the data for a series of films of different thicknesses. A striking reversal in polarity of the signals for thicker films was observed.
Preliminary results for the generation of coherent phonon pulses in multilayer metal structures show that electron diffusion must be taken into account in order to explain the observed acoustic echoes.
Related theoretical work was successful in elucidating the way light is modulated by strain on reflection or transmission through a multilayer structure. This can be done not only for longitudinal coherent phonons but also for shear coherent phonons.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A)., HOKKAIDO UNIVERSITY, Coinvestigator not use grants, Competitive research funding, 11305008

INVESTIGATION OF RIGIDITY PERCOLATION, MEDIUM-RANGE STRUCTURES AND FRACTON IN MULTI-COMPOUND GLASSY SEMICONDUCTORS
Grants-in-Aid for Scientific Research
1997 - 2000
MURASE Kazuo, MATSUDA Osamu, INOUE Koichi, WANG Yong
We have presented a comprehensive study of the roles of nanoscopic structural units in chalcogenide glasses in relaxation behaviors around glass transition temperature, structural changes toward crystallization, electronic structures around band-tails, and relaxation processes of photoexcited carriers.
First, we have shown that the variation of Se_n (n>2) chain segments essentially determines relaxational behaviors of networks. We have also shown that the compositional dependence of resonant Raman spectra is explained by the variation in lengths of the Se_n chain and the CST chain. Second, we have found that intrinsic inhomogeneity in Ge-Ge ethan-like units, Se-Se bonds, and fragments similar to β-GeSe_2 can cause significantly different macroscopic structural changes in GeSe_2 glass. Finally, we have demonstrated that threefold-coordinated Se atoms forming Se-Se bonds play a key role in the photoinduced structural change and the dynamics of photoexcited carriers in GeSe_2 glass.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B)., OSAKA UNIVERSITY, Coinvestigator not use grants, Competitive research funding, 09440117

アモルファスカルコゲナイド半導体における異方性光誘起構造変化現象の研究
科学研究費助成事業
1998 - 1999
松田 理
物質の準安定状態であるガラス状態は、通常、熱的な励起により、安定な結晶状態に移行する。アモルファスカルコゲナイド半導体ではこの転移を光照射によって起こすことができる。光には偏光方向の自由度があるので、このような構造変化にかかわる特徴的な方向(例えば結晶軸)を励起光の偏向方向によって制御できる可能性がある。本研究では、光誘起構造変化現象における光励起状態の緩和過程の果たす役割について調べる。
アモルファスカルコゲナイド半導体における、光励起直後の電子励起状態の緩和過程を調べることを目指して。フェムト秒光パルスを用いたポンププローブ超高速過渡的反射率変化測定装置を組み立てた。この測定装置に用いる新しい共通パス型の干渉計を開発した。本装置により試料のピコ秒時間領域の反射率変化および表面変位を検出することができる。
装置の評価のためにアモルファスSi薄膜についての測定を行った。結果を定量的に理解するために、薄膜試料内での熱伝搬、超音波伝搬、電子格子相互作用を考慮したモデルの構築を行った。また、等方的なアモルファス物質中に光によって誘起される非等方的な誘電率変化を検出するための実験配置について詳しい検討を行った。
日本学術振興会, 奨励研究(A), 北海道大学, Principal investigator, Competitive research funding, 10740149

Ultra high frequency phonon pulse generation and detection in solids and liquids　　　　　　　　　　　　　　　
1998
Competitive research funding

Exciton relaxation in chalcogenide semiconductor investigated by time-resolved photoluminescence measurement
Grants-in-Aid for Scientific Research
1995 - 1996
MATSUDA Osamu, INOUE Koichi
Amorphous chalcogenide semiconductors which contain the elements of group VI show various kinds of photo-induced structural changes such as photo-darkening, photo-bleaching, photo-crystallization, etc.. These changes are caused by lattice deformations which result from the relaxation of the photo-excited electrons through the strong electron-phonon interaction. It is also important that the amorphous states are not in the thermal equilibrium. The chalcogen atoms which are in two-fold coordinated are considered to play an important role, but the details of the mechanism is still not clear. For example, it is still unknown how the excited electron distorts the lattice.
To know the relaxation process of the excited electron in the amorphous and crystalline GeSe_2 which is a typical chalcogenide semiconductor, the time resolved photo-luminescence measurement was carried out. Both phases have the band-gap in visible region (2.2-2.7eV). The excitation by band-gap light causes a broad Gaussian-shaped photo-luminescence in near-infra-red region (-1eV). The large Stokes-shift is due to the strong electron-phonon interaction. The continuous wave laser light is modulated by an acousto-optic modulator and then used for the excitation source of the time-resolved measurement. The measured time region was 100ns-3ms after the cut-off of the excitation light. There are many similarities in the spectral shape between the amorphous and crystalline GeSe_2. This result shows that the initial states of the luminescence are similar in both materials. As for the time-profile, the crystalline GeSe_2 shows the single exponential decay, while the amorphous GeSe_2 shows the extended exponential decay. The later is caused by the energy distribution of the luminescent centers by structural fluctuation in the glass.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Osaka University, Principal investigator, Competitive research funding, 07640445

カルコゲナイド半導体の励起緩和過程の研究
科学研究費助成事業
1992 - 1992
松田 理
日本学術振興会, 奨励研究(A), 大阪大学, 04740168