研究者データベース

森田 隆二(モリタ リユウジ)
工学研究院 応用物理学部門 光波動量子物理工学分野
教授

基本情報

所属

  • 工学研究院 応用物理学部門 光波動量子物理工学分野

職名

  • 教授

学位

  • 工学博士

J-Global ID

研究キーワード

  • 量子光科学   非線形光学   Ultrafast Optics   Nonlinear Optics   

研究分野

  • 自然科学一般 / 半導体、光物性、原子物理
  • ナノテク・材料 / 光工学、光量子科学

担当教育組織

職歴

  • 2005年 - 現在 - 北海道大学大学院工学研究院 応用物理学部門 教授
  • 2017年04月 - 2019年03月 École Normale Supérieure Paris-Saclay, Laboratoire de Photonique Quantique et Moléculaire, Institut d'Alembert, Invited Professor

所属学協会

  • 日本物理学会   レーザー学会   Optica (formerly Optical Society)   応用物理学会   European Physical Society   

研究活動情報

論文

  • Yasunori Toda, Satoshi Tsuchiya, Keisaku Yamane, Ryuji Morita, Migaku Oda, Tohru Kurosawa, Tomaz Mertelj, Dragan Mihailovic
    Optics Express 31 11 17537 - 17537 2023年05月10日 [査読有り]
     
    We report an experimental approach to produce spatially localized photoinduced superconducting state in a cuprate superconductor using optical vortices with ultrafast pulses. The measurements were carried out using coaxially aligned three-pulse time-resolved spectroscopy, in which an intense vortex pulse was used for coherent quenching of superconductivity and the resulting spatially modulated metastable states were analyzed by the pump-probe spectroscopy. The transient response after quenching shows a spatially localized superconducting state that remains unquenched at the dark core of the vortex beam for a few picoseconds. Because the quenching is instantaneously driven by photoexcited quasiparticles, the vortex beam profile can be transferred directly to the electron system. By using the optical vortex-induced superconductor, we demonstrate spatially resolved imaging of the superconducting response and show that the spatial resolution can be improved using the same principle as that of super-resolution microscopy for fluorescent molecules. The demonstration of spatially controlled photoinduced superconductivity is significant for establishing a new method for exploring novel photoinduced phenomena and applications in ultrafast optical devices.
  • Haruki Kawaguchi, Kanta Takahashi, Rong Wei, Keisaku Yamane, Ken-ichi Yuyama, Satoyuki Kawano, Ryuji Morita, Nobuyuki Aoki, Katsuhiko Miyamoto, Takashige Omatsu
    Optical Manipulation and Structured Materials Conference (OMC 2022) 2022年12月08日
  • Asami Honda, Keisaku Yamane, Kohei Iwasa, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    Scientific reports 12 1 18674 - 18674 2022年11月04日 [査読有り]
  • Asami Honda, Keisaku Yamane, Kohei Iwasa, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    Scientific reports 12 1 14991/1 - 12 2022年09月02日 [査読有り]
     
    As an extension of pulse shaping techniques using the space-time coupling of ultrashort pulses or chirped pulses, we demonstrated the ultrafast beam pattern modulation by the superposition of chirped optical vortex pulses with orthogonal spatial modes. The stable and robust modulations with a modulation frequency of sub-THz were carried out by using the precise phase control technique of the constituent pulses in both the spatial and time/frequency domains. The performed modulations were ultrafast ring-shaped optical lattice modulation with 2, 4 and 6 petals, and beam pattern modulations in the radial direction. The simple linear fringe modulation was also demonstrated with chirped spatially Gaussian pulses. While the input pulse energy of the pulses to be modulated was 360 [Formula: see text]J, the output pulse energy of the modulated pulses was 115 [Formula: see text]J with the conversion efficiency of [Formula: see text] 32%. Demonstrating the superposition of orthogonal spatial modes in several ways, this ultrafast beam pattern modulation technique with high intensity can be applicable to the spatially coherent excitation of quasi-particles or collective excitation of charge and spin with dynamic degrees of freedom. Furthermore, we analyzed the Poynting vector and OAM of the composed chirped OV pulses. Although the ring-shaped optical lattice composed of OV pulse with topological charges of [Formula: see text] is rotated in a sub-THz frequency, the net orbital angular momentum (OAM) averaged over one optical period is found to be negligible. Hence, it is necessary to require careful attention to the application of the OAM transfer interaction with matter by employing such rotating ring-shaped optical lattices.
  • Takashige Omatsu, Katsuhiko Miyamoto, Ken-Ichi Yuyama, Keisaku Yamane, Ryuji Morita
    Journal of Photochemistry and Photobiology C: Photochemistry Reviews 52 100535/1 - 13 2022年09月 [査読有り]
  • Haruki Kawaguchi, Rong Wei, Keisaku Yamane, Ken-ichi Yuyama, Satoyuki Kawano, Ryuji Morita, Kohei Toyoda, Katsuhiko Miyamoto, Takashige Omatsu
    Conference on Lasers and Electro-Optics 2022年 
    We demonstrate the direct printing of an ultrafine microdot formed of gold nanoparticles by employing optical vortex laser induced forward transfer. Spin and orbital angular momentum induces the close-packing and sintering of gold nanoparticles.
  • Asami Honda, Keisaku Yamane, Masato Suzuki, Jin Kawaguchi, Yasunori Toda, Takashige Omatsu, Ryuji Morita
    2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings 2022年 
    We demonstrated ultrafast snapshot imaging with a sub-GHz framerate on the basis of our newly proposed recirculation-filtering method, which enables us to generate a wavelength-division multiplexed pulse train with a time interval in nanosecond regime.
  • Masato Suzuki, Keisaku Yamane, Takashige Omatsu, Ryuji Morita
    NEW JOURNAL OF PHYSICS 23 11 113043/1 - 11 2021年11月 
    We propose and demonstrate a novel vortex Airy beam which is a superposition of an Airy beam and its laterally sheared beam with a pi/2 phase shift. This new-type of vortex Airy beam exhibits stable propagation dynamics, wherein its singular point closely follows its main lobe, unlike conventional vortex Airy beams. Notably, the orbital angular mode purity of this new vortex Airy beam is up to 10% better than that of a conventional vortex Airy beam. We anticipate that this new type of vortex Airy beam, which combines the characteristics of an optical vortex and a diffraction-free Airy beam, will facilitate new directions in applications such as microscopy, material processing and nonlinear optics.
  • Haruki Kawaguchi, Kei Umesato, Kanta Takahashi, Keisaku Yamane, Ryuji Morita, Ken-ichi Yuyama, Satoyuki Kawano, Katsuhiko Miyamoto, Michinari Kohri, Takashige Omatsu
    Nanophotonics 11 4 855 - 864 2021年10月20日 [査読有り]
     
    Abstract An optical vortex possesses a ring-shaped spatial profile and orbital angular momentum (OAM) owing to its helical wavefront. This form of structured light has garnered significant attention in recent years, and it has enabled new investigations in fundamental physics and applications. One such exciting application is laser-based material transfer for nano-/micro-fabrication. In this work, we demonstrate the application of a single-pulse optical vortex laser beam for direct printing of ring-shaped structures composed of hexagonal close-packed, mono-/multi-layered nanoparticles which exhibit ‘structural color’. We compare and contrast the interaction of the vortex beam with both dielectric and metallic nanoparticles and offer physical insight into how the OAM of vortex beams interacts with matter. The demonstrated technique holds promise for not only photonic-based nano-/micro-fabrication, but also as a means of sorting particles on the nanoscale, a technology which we term ‘optical vortex nanoparticle sorting’.
  • Kazuhiko Oka, Keisaku Yamane, Moritsugu Sakamoto, Ryuji Morita
    Proceedings of SPIE - The International Society for Optical Engineering 11927 2021年 
    Spectroscopic polarization measurement and control using channeled spectrum has several unique features and is useful for various spectroscopic instruments. It utilizes the strong dispersion characteristics in polarization retardation of high-order retarders so that the polarization modulation can be made without using mechanical or active elements for polarization modulation. In this presentation, we describe its principle, basic features, and several applications including a spectroscopic ellipsometer and ultrafast rotations of beam profile and polarization.
  • 飯塚健介, 山根啓作, 川村一貴, 坂本盛嗣, 小野浩司, 岡和彦, 戸田泰則, 森田隆二
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 68th 2021年
  • Kohki Nakagawa, Keisaku Yamane, Ryuji Morita, Yasunori Toda
    APPLIED PHYSICS EXPRESS 13 4 042001/1 - 5 2020年04月 [査読有り][通常論文]
     
    Laguerre-Gaussian (LG) vortex mode generations are demonstrated by employing the optical injection of a higher-order transverse mode into a vertical cavity surface emitting laser. In addition to the coherent LG injection, Hermite-Gaussian (HG) injection also enable LG mode generation, where the chirality is controllable by the HG mode angle of the injection beam. The result can be well understood when we consider the astigmatic Gouy phase shifts within the microcavity. HG induced vortex generation eases the symmetrical requirements of the cavity and thus extends flexibility as regards the design and fabrication of vortex lasers.
  • Ablimit Ablez, Kohei Toyoda, Katsuhiko Miyamoto, Ryuji Morita, Takashige Omatsu
    OPTICAL MANIPULATION AND STRUCTURED MATERIALS CONFERENCE 2020 11522 2020年 
    We investigate the structures on a silicon (111) substrate produced by illumination of optical vortex. The fabricated structures on silicon (111) exhibit polycrystalline properties associated with rather complicated 7x7 constructed surface.
  • Rin Sasaki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda, Takashige Omatsu, Ryuji Morita
    OPTICAL MANIPULATION AND STRUCTURED MATERIALS CONFERENCE 2020 11522 2020年 
    We demonstrated that ultrafast azimuth rotation of linearly polarized beam by use of a chirped optical pulse pair, and the rotational frequency of sub-THz was realized.
  • Takashige Omatsu, Katsuhiko Miyamoto, Kohei Toyoda, Ryuji Morita, Yoshihiko Arita, Kishan Dholakia
    ADVANCED OPTICAL MATERIALS 7 14 1801672/1 - 20 2019年07月 [査読有り][通常論文]
     
    Recent work has shown that irradiation with light possessing orbital angular momentum (OAM) and an associated phase singularity, that is an optical vortex, twists a variety of materials. These include silicon, azo-polymer, and even liquid-phase resins to form various helically structured materials. This article provides a review of the unique helical-structured materials created and the novel fundamental phenomena enabled by this interaction between both the spin angular momentum and the OAM of light with matter. Such light-induced helical-structured materials will potentially lead to advanced photonic devices, for instance, metamaterials for ultrasensitive detection and reactions for chiral chemical composites.
  • Masato Suzuki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    SCIENTIFIC REPORTS 9 9979/1 - 14 2019年07月 [査読有り][通常論文]
     
    We demonstrate a comprehensive quantitative analysis of vector beam states (VBSs) by using a vector field reconstruction (VFR) technique integrating interferometry and imaging polarimetry, where the analysis is given by a cylindrically polarized Laguerre-Gaussian (LG) mode expansion of VBSs. From test examples of cylindrically polarized LG mode beams, we obtain the complex amplitude distributions of VBSs and perform their quantitative evaluations both in radial and azimuthal directions. The results show that we generated (l, p) = (1, 0) LG radially polarized state with a high purity of 98%. We also argue that the cylindrically polarized LG modal decomposition is meaningful for the detail discussion of experimental results, such as analyses of mode purities and mode contaminations. Thus the VFR technique is significant for analyses of polarization structured beams generated by lasers and converters.
  • Keisaku Yamane, Kohei Iwasa, Rin Sasaki, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    Proceedings of SPIE - The International Society for Optical Engineering 11141 2019年 
    We developed the high-efficiency beam converter for ultrafast spatio-temporal control of light waves based on Sagnac interferometer. The flexible control both in the azimuth and radial directions in the ultrafast regime was also realized.
  • Y. Toda, K. Nakagawa, K. Yamane, R. Morita, Y. Awaji
    Proceedings of SPIE - The International Society for Optical Engineering 11141 2019年 
    Based on our previous work, in which we demonstrated single orbital angular momentum (OAM) mode emissions from a vertical cavity surface emitting laser (VCSEL) with an external optical feedback, the conditions of the vortex mode emission are investigated in terms of feedback efficiency and polarization. There are two orthogonal polarization configurations for efficient single OAM mode emission, one of which corresponds to the dominant polarization in freerunning VCSEL. Nearly identical emission properties of the two polarizations indicate an independence between the spin and OAM. On the other hand, the stability of the OAM mode emission, which is characterized by the dependencies of the feedback efficiency and injection current, is changed between the two polarizations, suggesting different contributions of the broken rotational symmetry to the spin and OAM.
  • Keisaku Yamane, Kohei Iwasa, Rin Sasaki, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC) Part F140-CLEO_Europe 2019 2019年 
    When two optical vortices with different topological charges mutually interfere, azimuthally periodic structure called a ring-shaped optical lattice is formed [1]. The petal-like beam profile can be flexibly rotated by controlling the intermodal phase difference, which offers us rotational degree of freedom in applications such as optical manipulations of micro/nano particles and micro machines. However, their maximum rotational frequency has been limited to GHz regime owing to their response time or bandwidth. Recently, we succeeded in drastically increasing the rotational frequency up to THz regime by introducing a new technique based on spatial mode multiplexing of chirped optical-vortex pair [2].
  • Keisaku Yamane, Yuho Watanabe, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC) Part F140-CLEO_Europe 2019 2019年 
    Recently, the spatial mode multiplexing based on optical vortices (OVs) attracts much attentions as a promissing technology for high-capacity optical communications. For such OV-based telecommunications, optical components for mode decomposition with respect to azimuth mode indices (topological charges) - so-called orbital angular momentum (OAM) sorters - are key devices, and various kinds of OAM sorters have been demonstrated such as computer-generated holograms as far. Among them, the geometric transformation (GT) technique has great advantages that the insertion loss is quite low and it supports inverse transformation (multiplexing) [1]. In earlier studies, GT-based OAM sorters have been realized by using spatial light modulators (SLMs) [1], and more recently, transparent refractive elements produced by using such as diamond machining [2] and Pancharatnam Berry phase [3] have been demonstrated. However, the GT-based method has the serious disadvantage of relatively large crosstalk between the neighboring modes. In order to overcome the problems, the beam copying technique by using diffractive optics was demonstrated [4]. The novel technique can greatly reduce the crosstalk between the OAM modes, but spoils the advantage that the OAM sorter can support the low-loss inverse transformation. In this paper, we demonstrate the new beam duplication technique by using a Sagnac interferometer, which can improve the resolution in the OAM mode decomposition and also support low-loss inverse transformation.
  • Masato Suzuki, Keisaku Yamane, Moritsugu Sakamoto, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    OPTICS EXPRESS 26 3 2584 - 2598 2018年02月 [査読有り][通常論文]
     
    We proposed and constructed a system to realize broadband generation of arbitrary axisymmetrically polarized (AP) pulses with spatial complex amplitude modulation. This system employs the combination of a spatial light modulator in the 4-f configuration (4-f SLM), and a space variant wave plate as a common path interferometer. The 4-f SLM and the common path interferometer offer compensation for spatial dispersion with respect to wavelength and stability to perturbation, respectively. We experimentally demonstrated the various AP pulses generation by applying modulations of fundamental and higher-order Laguerre-Gauss modes, whose radial indices were, respectively, p = 0 and 1, with high purity, which showed that we were able to generate arbitral AP pulses with spatial complex amplitude modulation. This technique is expected to be applied in both classical and quantum communications with higher-order modes. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
  • Keisaku Yamane, Yuho Watanabe, Isamu Wakisaka, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    Optics InfoBase Conference Papers Part F114-FIO 2018 2018年 
    New mode decomposition devices for optical vortices were developed. Their performances were experimentally verified and in good agreement with the corresponding simulations, showing precise spatial-phase control based on Pancharatnam-Berry phase.
  • Ryuji Morita, Masato Suzuki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda
    COMPLEX LIGHT AND OPTICAL FORCES XII 10549 2018年 [査読有り][通常論文]
     
    Subsequently to the previous generation of ultrashort and ultra-broadband optical-vortex (OV) pulses (pulse energy: several tens of mu J) in few-cycle regime, we performed the generation of axisymmetrically polarized pulses with spatial complex amplitude modulation, which is suitable for a broadband spectrum. The generation system employs the combination of spatial light modulators in the 4-f configuration and a space variant wave plate as a common path interferometer. The spatial light modulators in the 4-f configuration offer the spatial dispersion compensation with respect to wavelength; in addition, the common path interferometer provides the stability to perturbation. We experimentally demonstrated the generation of various axisymmetrically polarized pulses by applying modulations of fundamental and higher-order Laguerre-Gauss modes with high purity. The experimental results show that we are able to generate arbitral axisymmetrically polarized pulses with spatial complex amplitude modulation.
  • 山根 啓作, 森田 隆二
    光アライアンス 28 9 31 - 35 日本工業出版 2017年09月 [査読無し][通常論文]
  • Y. Toda, A. Moriya, K. Yamane, R. Morita, K. Shigematsu, Y. Awaji
    APPLIED PHYSICS LETTERS 111 10 101102/1 - 5 2017年09月 [査読有り][通常論文]
     
    The single orbital angular momentum mode emission from a commercially available broad-area vertical cavity surface emitting laser (VCSEL) is realized with an optical feedback technique using a spatial light modulator, where a computer generated hologram (CGH) is optimized by taking into account the mode properties of the external cavity VCSEL. The flexibility with which the chirality of the orbital angular momentum mode can be selected is also demonstrated simply by changing the chirality of the CGH. The technique is very simple and easily applicable to other VCSELs without processing. (C) 2017 Author(s).
  • Takashige Omatsu, Natalia M. Litchinitser, Etienne Brasselet, Ryuji Morita, Jian Wang
    OPTICS EXPRESS 25 14 16681 - 16685 2017年07月 [査読有り][通常論文]
     
    Structured light beams, such as optical vortices, vector beams, and non-diffracting beams, have been recently studied in a variety of fields, such as optical manipulations, optical telecommunications, nonlinear interactions, quantum physics, and 'super resolution' microscopy.. Their unique physical properties, such as annular intensity profile, helical wavefront and orbital angular momentum, give rise to a plethora of new, fundamental light-matter interactions and device applications. Recent progress in nanostructured materials, including metamaterials and metasurfaces, opened new opportunities for structured light generation on the microscale that exceed the capabilities of bulk-optics approaches such as computer generated holography and diffractive optics. Furthermore, structured optical fields may interact with matters on the subwavelength scale to yield new physical effects, such as spin-orbital momentum coupling. This special issue of Optics Express focuses on the state-of-the-art fundamental research and emerging technologies and applications enabled by the interplay of "structured light" and "structured materials". (C) 2017 Optical Society of America
  • Y. Toda, H. Moriya, K. Shigematsu, K. Yamane, R. Morita, Y. Awaji
    OPTICAL MANIPULATION CONFERENCE 10252 2017年 [査読有り][通常論文]
     
    Single angular momentum (OAM) mode emissions from a vertical cavity surface emitting laser (VCSEL) were demonstrated by an external optical feedback using computer generated holograms, which are optimized on the OAM modal gain of the free-running VCSEL. Side-mode suppression ratio of more than 23 dB was achieved for the OAM modes with l = +/- 1.
  • Kai Izumisawa, Ablimit Ablez, Yuri Nakamura, Tatsuyuki Sugimoto, Honami Fujiwara, Katsuhiko Miyamoto, Ryuji Morita, Takashige Omatsu
    OPTICAL MANIPULATION CONFERENCE 10252 2017年 [査読有り][通常論文]
     
    We reported on crystalline silicon structures formed on a silicon (111) substrate through picosecond optical vortex pulse illumination. A crystalline silicon needle with a height of 20 mu m was structured through single vortex pulse illumination. Sixteen overlaid vortex pulses shaped the silicon into a crystalline pillar with a height of similar to 45 mu m.
  • Keisaku Yamane, Kohei Iwasa, Kohei Kakizawa, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC) 2017年 [査読有り][通常論文]
  • Kai Izumisawa, Tatsuyuki Sugimoto, Yuri Nakamura, Katsuhiko Miyamoto, Tsukasa Torimoto, Ryuji Morita, Takashige Omatsu
    OPTICAL MANIPULATION CONFERENCE 10252 2017年 [査読有り][通常論文]
     
    We reported on a plasmonic metal Au nano-needle by nanosecond optical vortex pulse illumination. The Au nano-needle with a tip-diameter of < 100 nm was structured by illumination of a single vortex pulse.
  • Keisaku Yamane, Kohei Iwasa, Kohei Kakizawa, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    OPTICAL MANIPULATION CONFERENCE 10252 2017年 [査読有り][通常論文]
     
    A new method for the ultrafast rotation of ring-shaped optical lattices based on frequency-chirping of optical pulses was demonstrated in THz regime, which is three orders of magnitude faster than those by the conventional methods. Our optical lattice generator with a spatial light modulator is robust thanks to the 4-f configuration and enables us to flexibly control their rotational symmetry. The generated ultrafast-rotating ring-shaped optical lattices with a rotational frequency of 0.59 THz were successfully boosted from 5 mu J up to 125 mu J by using a home-built 4-pass Ti:sapphire amplifier without any limitation by optical damage to the spatial light modulator.
  • Kyohhei Shigematsu, Masato Suzuki, Keisaku Yamane, Ryuji Morita, Yasunori Toda
    APPLIED PHYSICS EXPRESS 9 12 122401/1 - 4 2016年12月 [査読有り][通常論文]
     
    By using radially polarized pulses for excitation in degenerate four-wave mixing (DFWM) spectroscopy, we realize highly sensitive snap-shot measurement of optical anisotropies in semiconductor films. Because the radially polarized pulses exhibit spatially varying linear polarizations, the optical anisotropies in samples can be evaluated from the spatial distributions of DFWM signals without rotating the polarization of the excitation pulses. We measure the excitons in GaN layers and evaluate the energies of uniaxial strain and the spin-exchange interaction constant. Our results prove both the accuracy and sensitivity of the snap-shot measurement. (C) 2016 The Japan Society of Applied Physics
  • Masato Suzuki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    PHYSICAL REVIEW A 94 4 043851/1 - 7 2016年10月 [査読有り][通常論文]
     
    We derived the Berry connection of vector vortex states (VVSs) from the "true" Hamiltonian obtained through the Maxwell-Schrodinger equation for an inhomogeneous anisotropic (IA) medium, and we experimentally demonstrated measurement of the corresponding Pancharatnam-Berry (PB) geometrical phase of VVSs. The PB phase (PBP) of VVSs can be divided into two phases: homogeneous and inhomogeneous PBPs. Homogeneous and inhomogeneous PBPs are related to the conventional PBP and the spatially dependent geometric phase given by an IA medium such as a polarization converter, respectively. We theoretically detected that inhomogeneous PBP accumulation originates from the gauge dependence of the index of the hybrid-order Poincare sphere, which provides an alternate method for understanding optical spin-orbital angular momentum conversion. The homogeneous PBP, which is explicitly observed, has implications for quantum-statemanipulation and information processing.
  • K. Yamane, M. Sakamoto, N. Murakami, R. Morita, K. Oka
    OPTICS LETTERS 41 19 4597 - 4600 2016年10月 [査読有り][通常論文]
     
    A novel method of ultrafast rotation of a ring-shaped optical lattice in the picosecond time region was proposed and demonstrated. Our ring-lattice generator was assembled by a pair of linearly chirped pulses with a time delay, a high-order birefringent retarder, and an axially symmetric polarization element. Using a mode-locked Ti:sapphire laser oscillator as a light source, stable two-, four-, and six-petaled ring-lattice rotations were demonstrated with the rotation periods of 1.6, 3.2, and 4.8 ps, respectively. Our method has the potential to open up a new technique to resonantly excite propagating quasi- particles together with their coherent enhancement. (C) 2016 Optical Society of America
  • 森田 隆二
    応用物理 85 5 396 - 403 応用物理学会 2016年05月 [査読有り][招待有り]
  • Fuyuto Takahashi, Shun Takizawa, Hirofumi Hidai, Katsuhiko Miyamoto, Ryuji Morita, Takashige Omatsu
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 213 4 1063 - 1068 2016年04月 [査読有り][通常論文]
     
    We discovered that a nanosecond optical vortex pulse can create a chiral cone-shaped monocrystalline silicon (Si) nanostructure (chiral Si nanocone) by transferring its optical angular momentum to a monocrystalline Si substrate. The fabricated Si nanocone, with a length of 4.8 mu m and a tip curvature of approximate to 110nm, was fully monocrystalline, and it had a spiral structure with an 86nm line width on a conical surface. Furthermore, its chirality was also determined directly from the handedness of the optical vortex pulse. Such chiral Si nanocones may enable the development of novel silicon photonic devices as well as ultra-highly efficient photovoltaic devices.
  • Fuyuto Takahashi, Katsuhiko Miyamoto, Hirofumi Hidai, Keisaku Yamane, Ryuji Morita, Takashige Omatsu
    SCIENTIFIC REPORTS 6 21738/1 - 10 2016年02月 [査読有り][通常論文]
     
    The formation of a monocrystalline silicon needle by picosecond optical vortex pulse illumination was demonstrated for the first time in this study. The dynamics of this silicon needle formation was further revealed by employing an ultrahigh-speed camera. The melted silicon was collected through picosecond pulse deposition to the dark core of the optical vortex, forming the silicon needle on a submicrosecond time scale. The needle was composed of monocrystalline silicon with the same lattice index (100) as that of the silicon substrate, and had a height of approximately 14 mu m and a thickness of approximately 3 mu m. Overlaid vortex pulses allowed the needle to be shaped with a height of approximately 40 mu m without any changes to the crystalline properties. Such a monocrystalline silicon needle can be applied to devices in many fields, such as core-shell structures for silicon photonics and photovoltaic devices as well as nano- or microelectromechanical systems.
  • 内古閑 隆太郎, 重松 恭平, 山根 啓作, 森田 隆二, 戸田 泰則
    日本物理学会講演概要集 71 2 1414 - 1414 一般社団法人 日本物理学会 2016年 

    ビーム断面上の偏光分布が二回対称で、直線偏光と円偏光を同時に持つポアンカレビームパルスを励起光に用いると、異なるスピン状態を持つ励起子の同時励起が可能である。本研究では、縮退四光波混合分光を用いたバルクGaN励起子励起およびストークス分解検出を行い、励起子スピンのコヒーレントダイナミクス測定を実現した。得られた信号光の空間偏光分布はT2時間内で励起光を良く反映しており、励起子スピンのコヒーレント状態保持を示すことができた。

  • Fuyuto Takahashi, Honami Fujiwara, Kai Izumisawa, Katsuhiko Miyamoto, Hirofumi Hidai, Ryuji Morita, Takashige Omatsu
    2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2016年 [査読有り][通常論文]
     
    Optical vortex illumination enables the creation of silicon needles with a height of similar to 14 mu m and a thickness of similar to 2 mu m. Silicon needle formation requires an optical vortex pulse with a pulse duration of 10 similar to 20 ps, so as to create thermally-melted silicon with fewer heat diffusion effects.
  • K. Shigematsu, K. Yamane, R. Morita, Y. Toda
    PHYSICAL REVIEW B 93 4 045205/1 - 8 2016年01月 [査読有り][通常論文]
     
    The coherent dynamics of the exciton center-of-mass motion in bulk GaN are studied using degenerate four-wave-mixing (FWM) spectroscopy with Laguerre-Gaussian (LG) mode pulses. We evaluate the exciton orbital angular momentum (OAM) dynamics from the degree of OAM, which is derived from the distributions of OAM (topological charge) of the FWM signals. When excitons are excited with two single-mode LG pulses, the exciton OAM decay time significantly exceeds the exciton dephasing time, which can be attributed to high uniformity of the exciton dephasing in our bulk sample because the decoherence of the exciton OAM is governed by the angular variation in the exciton dephasing. We also analyze the topological charge (l) dependence of the OAM decay using a multiple-mode LG pump pulse, which allows us to simultaneously observe the dynamics of the exciton OAM for different l values under the same excitation conditions. The OAM decay times of the l = 1 component are usually longer than those of the l = 0 component. The l-dependent OAM decay is supported by a phenomenological model which takes into account the local nonuniformity of the exciton dephasing.
  • Masato Suzuki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    SCIENTIFIC REPORTS 5 17797/1 - 9 2015年12月 [査読有り][通常論文]
     
    Cylindrically polarized (CP) modes are laser beam modes which have rotational symmetry of the polarization distribution around the beam axis. Considerable attention has been paid to CP modes for their various applications. In this paper, by using the extended Stokes parameters and the degree of polarization defined for the spatial distribution (DOP-SD), we fully-quantitatively characterize the spectrally-resolved polarization states of arbitrary CP (axisymmetrically polarized and higher-order cylindrically polarized) broadband pulses generated by coherent beam combining. All the generated pulse states were fully-quantitatively analyzed for the first time and proved to have high symmetry (DOP-SD greater than or similar to 0.95) and low spectral dependence of polarization states. Moreover, we show the DOP-SD, which cannot be defined by the conventional higher-order and hybrid Stokes parameters, enables us to make a quantitative evaluation of small degradation of rotational symmetry of polarization distribution. This quantitative characterization with high precision is significant for applications of precise material processing, quantum information processing, magneto-optical storage and nonlinear spectroscopic polarimetry.
  • Masato Suzuki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    OPTICAL REVIEW 22 1 179 - 183 2015年02月 [査読有り][通常論文]
     
    The extended Stokes parameters for arbitrary cylindrically polarized beams are newly introduced to evaluate their quality. A set of the parameters, expressing a cylindrically polarized state, permits the definition of the degree of polarization that indicates the purity of the spatial symmetry of polarization of a light beam. In addition, the Pancharatnam-Berry phase related to the cylindrically polarized states is described by the new Stokes parameters.
  • Moritsugu Sakamoto, Ryohei Fukumoto, Naoshi Murakami, Ryuji Morita, Kazuhiko Oka
    OPTICAL REVIEW 22 1 174 - 178 2015年02月 [査読有り][通常論文]
     
    We present the topological-charge-dispersion reduction scheme in optical vortex generation using axially symmetric half-wave plates (AHPs). The topological-charge dispersion caused by retardation errors of AHPs and other waveplates is decreased by eliminating unwanted circular-polarization components.
  • Masato Suzuki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2015年 [査読有り][通常論文]
     
    By using the extended Stokes parameters and the degree of polarization defined for the spatial distribution (DOP-SD), we fully quantitatively characterize the polarization states of arbitrary (DOP-SD> 0.96) axisymmetrically-polarized femtosecond pulses generated by coherent beam combining. (C) 2014 Optical Society of America
  • 岡 和彦, 坂本 盛嗣, 山根 啓作, 森田 隆二
    O plus E 37 4 263 - 268 2015年 [査読有り][招待有り]
  • Keisaku Yamane, Asami Honda, Yasunori Toda, Ryuji Morita
    ULTRAFAST PHENOMENA XIX 162 809 - 812 2015年 [査読有り][通常論文]
     
    We demonstrated the generation of over 1-mJ intense optical-vortex pulses of which topological charges were programmable controlled by computer-generated holograms. The pulse duration was characterized to be 27 fs by two-dimensional spectral shearing interferometry.
  • Takashige Omatsu, Ryuji Morita
    Singular and Chiral Nanoplasmonics 311 - 334 2014年11月30日 [査読有り][通常論文]
  • Masato Suzuki, Keisaku Yamane, Kazuhiko Oka, Yasunori Toda, Ryuji Morita
    OPTICS EXPRESS 22 14 16903 - 16915 2014年07月 [査読有り][通常論文]
     
    Nonlinear propagation of focused axisymmetrically-polarized ultrashort optical pulses along the optic axis in a uniaxial crystal is investigated experimentally and theoretically. The energy transfer between an azimuthally-polarized pulse and a radially-polarized pulse is observed. To analyze the nonlinear propagation, a general paraxial equation with a third-order nonlinearity for axisymmetrically-polarized pulses in a uniaxial crystal is derived and the extended Stokes parameters (ESPs) based on cylindrical coordinates are newly-introduced. The simulation results by using this equation, providing the calculated ESPs, well explain our experimental observations: 1) the energy transfer is attributed to the four-wave-mixing effect, reflecting the overlapping between the axisymmetrically polarized modes, 2) the variations of the polarization defined from the ESPs are clarified to be affected by the self-and the cross-phase modulations, which make the effective propagation length long or short. (C) 2014 Optical Society of America
  • Keisaku Yamane, Zhili Yang, Yasunori Toda, Ryuji Morita
    NEW JOURNAL OF PHYSICS 16 053020/1 - 15 2014年05月 [査読有り][通常論文]
     
    We propose a high-precision method for measuring the orbital angular momentum (OAM) spectrum of ultra-broadband optical-vortex (OV) pulses from fork-like interferograms between OV pulses and a reference plane-wave pulse. It is based on spatial reconstruction of the electric fields of the pulses to be measured from the frequency-resolved interference pattern. Our method is demonstrated experimentally by obtaining the OAM spectra for different spectral components of the OV pulses, enabling us to characterize the frequency dispersion of the topological charge of the OAM spectrum by a simple experimental setup. Retrieval is carried out in quasi-real time, allowing us to investigate OAM spectra dynamically. Furthermore, we determine the relative phases (including the sign) of the topological-charge-resolved electric-field amplitudes, which are significant for evaluating OVs or OV pulses with arbitrarily superposed modes.
  • Kyohhei Shigematsu, Keisaku Yamane, Ryuji Morita, Yasunori Toda
    2014 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2014年 [査読有り][通常論文]
     
    The spatiotemporal coherence of excitons is investigated by degenerate four-wavemixing using optical vortices with multiple orbital angular momentum (OAM). The OAM-resolved signal indicates that the topological phase with large OAM is robust against spatial decoherence.
  • Fuyuto Takahashi, Shun Takizawa, Hirofumi Hidai, Katsuhiko Miyamoto, Ryuji Morita, Takashige Omatsu
    2014 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2014年 [査読有り][通常論文]
     
    We for the first time demonstrated a chiral mono-crystalline cone-shaped silicon structure (chiral Si nano-cone). It was fabricated on a nano-scale by transferring the optical angular momentum of optical vortex to a mono-crystalline Si substrate.
  • Keisaku Yamane, Yasuyuki Shioda, Masato Suzuki, Yasunori Toda, Ryuji Morita
    2014 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2014年 [査読有り][通常論文]
     
    We demonstrated the generation of ultra-broadband optical pulses with axially-symmetric polarization, on the basis of a coherent beam combining technique. The high polarization purity (similar to 95 %) ranging from 750 to 880 nm was obtained. (C) 2014 Optical Society of America
  • Ryuji Morita, Keisaku Yamane, Zhili Yang, Yasunori Toda
    COMPLEX LIGHT AND OPTICAL FORCES VIII 8999 2014年 [査読有り][通常論文]
     
    Subsequently to the previous generation of ultrashort and ultra-broadband optical-vortex (OV) pulses (pulse energy: several tens of mu J) in few-cycle regime, we demonstrate high-power OV pulse generation with topological charge flexibility by employing a 4-f OV converter and pre- and main-amplifications. Our configuration overcomes the low-throughput drawback of the vortex converter, simultaneously compensating for the angular dispersion. It also gives flexibility of OAM- or topological-charge control. Thus, we succeed in generation of mJ-class ultra-broadband OV pulses (similar to 790-similar to 820 nm) with a programmably-controlled topological charge. Moreover, we experimentally exhibit a high-precision method for measuring frequency-resolved OAM spectrum of femtosecond ultra-broadband OV pulses on the basis of electric-field reconstruction in the spatial domain. In addition, we present the generation of ultrashort pulses with axially-symmetric polarization by coherent beam combining of OVs.
  • 多幡 龍徳, 高橋 冬都, 滝澤 隼, 宮本 克彦, 森田 隆二, 尾松 孝茂
    レーザー研究 42 10 780 - 783 2014年 [査読有り][招待有り]
  • Moritsugu Sakamoto, Kazuhiko Oka, Ryuji Morita, Naoshi Murakami
    OPTICS LETTERS 38 18 3661 - 3664 2013年09月 [査読有り][通常論文]
     
    To overcome a trade-off issue between stability and flexibility in the generation of ring-shaped optical lattices, we proposed and demonstrated a novel generation method by using axially symmetric polarization elements. While two optical vortices were coaxially generated, electrically controlled phase difference between them by an electro-optic modulator enabled a precise rotation of the lattice. Our method has the capability to fulfill the high stability and rapid rotation. (C) 2013 Optical Society of America
  • Kyohhei Shigematsu, Yasunori Toda, Keisaku Yamane, Ryuji Morita
    JAPANESE JOURNAL OF APPLIED PHYSICS 52 8 08JL08/1 - 5 2013年08月 [査読有り][通常論文]
     
    We report on the coherent dynamics of the photoexcited orbital angular momentum (OAM) states of GaN excitons. The measurements were performed by a pump-probe four-wave mixing (FWM) using optical vortex (OV) pulses, where the pump OV pulse transfers its OAM to the center of mass momentum of excitons and the conversion of OAM via FWM with the probe pulse is detected. Especially, we performed analysis of the signal using an OAM-resolved spectroscopy, which allows us to evaluate the dephasing dynamics of excitons in time and space. The results indicate that near perfect conversion is achieved using the OV pulses with nonzero OAM and its spatial coherence remains high during the dephasing time, clearly indicating that the excitons keep the OAM transferred by the pump OV. In contrast, the component associated with the imperfect conversion becomes significant when one of the incident pulses intentionally includes an OAM-free component. The effect is clearly confirmed by the FWM excited by the pump with multiple OAM. (C) 2013 The Japan Society of Applied Physics
  • Kohei Toyoda, Fuyuto Takahashi, Shun Takizawa, Yu Tokizane, Katsuhiko Miyamoto, Ryuji Morita, Takashige Omatsu
    PHYSICAL REVIEW LETTERS 110 14 143603/1 - 5 2013年04月 [査読有り][通常論文]
     
    We discovered that chiral nanoneedles fabricated by vortex laser ablation can be used to visualize the helicity of an optical vortex. The orbital angular momentum of light determines the chirality of the nanoneedles, since it is transferred from the optical vortex to the metal. Only the spin angular momentum of the optical vortex can reinforce the helical structure of the created chiral nanoneedles. We also found that optical vortices with the same total angular momentum (defined as the sum of the orbital and spin angular momenta) are degenerate, and they generate nanoneedles with the same chirality and spiral frequency. DOI: 10.1103/PhysRevLett.110.143603
  • Masato Suzuki, Keisaku Yamane, Yasunori Toda, Ryuji Morita
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR) 2013年 [査読有り][通常論文]
     
    We investigate nonlinear propagation of ultrashort optical pulses with radially- and azimuthally-polarized modes in a uniaxial crystal. The energy exchange between the modes, ascribed to nonlinear four-wave-mixing effect with Gouy-phase shifts, is discussed.
  • Masato Suzuki, Keisaku Yamane, Yasunori Toda, Ryuji Morita
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE (CLEO EUROPE/IQEC) 2013年 [査読有り][通常論文]
  • Fuyuto Takahashi, Kohei Toyoda, Shun Takizawa, Katsuhiko Miyamoto, Ryuji Morita, Takashige Omatsu
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2013年 [査読有り][通常論文]
     
    We discovered that chiral-structure of nano-needles fabricated by optical vortex laser ablation can be controlled by changing the magnitude of orbital angular momentum. We also demonstrated the formation of a chiral Si-bump.
  • Shun Takizawa, Fuyuto Takahashi, Kohei Toyoda, Katsuhiko Miyamoto, Ryuji Morita, Takashige Omatsu
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE (CLEO EUROPE/IQEC) 2013年 [査読有り][通常論文]
  • Keisaku Yamane, Asami Honda, Kyohhei Shigematsu, Yasunori Toda, Ryuji Morita
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR) 2013年 [査読有り][通常論文]
     
    We demonstrate the optical parametric amplification of optical-vortex pulses with the programmable topological-charge control. Combination of optical-parametric amplification and 4-f configuration overcomes the low-throughput drawback of the vortex converter, simultaneously compensating for the angular dispersion.
  • Keisaku Yamane, Yasunori Toda, Ryuji Morita
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2013年 [査読有り][通常論文]
     
    We demonstrate the amplification of ultrashort optical-vortex pulses through the optical parametric process, where optical-vortex seed pulses with computer-controlled topological charges are employed. In this scheme, the low-throughput drawback of the vortex converter is overcome. (C) 2013 Optical Society of America
  • Zhili Yang, Keisaku Yamane, Yasunori Toda, Ryuji Morita
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR) 2013年 [査読有り][通常論文]
     
    We experimentally exhibit a high-precision method for measuring frequency-resolved orbital angular momentum (OAM) spectrum of femtosecond ultra-broadband optical-vortex pulses from fork-like interferograms. This method enables us to evaluate topological-charge dispersion of ultra-broadband optical-vortex pulses.
  • Zhili Yang, Keisaku Yamane, Yasunori Toda, Ryuji Morita
    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2013年 [査読有り][通常論文]
     
    We experimentally demonstrate a simple and high-precision method for measuring orbital angular momentum (OAM) spectra of femtosecond ultra-broadband optical-vortex pulses from fork-like interferograms. This method enables quasi-real-time OAM measurement for ultra-short or ultra-broadband optical vortices.
  • Y. Toda, K. Shigematsu, K. Yamane, R. Morita
    Optics Communications 308 147 - 151 2013年 [査読有り][通常論文]
     
    The orbital angular momentum (OAM) resolved spectroscopy is being applied to various research fields associated with optical vortices or Laguerre-Gaussian (LG) beams, in which the key technique is to convert LG beams to a fundamental Gaussian (HG≡HG00) beam. In this work, we propose a method to realize efficient mode conversion by using spiral phase modulations. Numerical simulations and experiments are carried out to compare our proposal with the standard technique using rotational phase modulations. The results reveal that our proposed method improves the uniformity of the conversion efficiency across various OAM, allowing us to obtain precise OAM spectra. © 2013 Elsevier B.V.
  • Keisaku Yamane, Yasunori Toda, Ryuji Morita
    OPTICS EXPRESS 20 17 18986 - 18993 2012年08月 [査読有り][通常論文]
     
    We generated a 2.3-cycle, 5.9-fs, 56-mu J ultrashort optical-vortex pulse (ranging from similar to 650 to similar to 950 nm) in few-cycle regime, by optical parametric amplification. It was performed even by using passive elements (a pair of prisms and chirped mirrors) for chirp compensation. Spectrally-resolved interferograms and intensity profiles showed that the obtained pulses have no spatial or topological-charge dispersion during the amplification process. To the best of our knowledge, it is the first generation of optical-vortex pulses in few-cycle regime. They can be powerful tools for ultrabroadband and/or ultrafast spectroscopy and experiments of high-intensity field physics. (C) 2012 Optical Society of America
  • Kohei Toyoda, Katsuhiko Miyamoto, Nobuyuki Aoki, Ryuji Morita, Takashige Omatsu
    NANO LETTERS 12 7 3645 - 3649 2012年07月 [査読有り][通常論文]
     
    We discovered for the first time that light can twist metal to control the chirality of metal nanostructures (hereafter, chiral metal nanoneedles). The helicity of optical vortices is transferred to the constituent elements of the irradiated material (mostly melted material), resulting in the formation of chiral metal nanoneedles. The chirality of these nanoneedles could be controlled by just changing the sign of the helicity of the optical vortex. The tip curvature of these chiral nanoneedles was measured to be <40 nm, which is less than 1/25th of the laser wavelength (1064 nm). Such chiral metal nanoneedles will enable us to selectively distinguish the chirality and optical activity of molecules and chemical composites on a nanoscale and they will provide chiral selectivity for nanoscale imaging systems (e.g., atomic force microscopes), chemical reactions on plasmonic nanostructures, and planar metamaterials.
  • Moritsugu Sakamoto, Kazuhiko Oka, Ryuji Morita
    COMPLEX LIGHT AND OPTICAL FORCES VI 8274 2012年 [査読有り][通常論文]
     
    We previously developed an achromatic method for the generation of the white-light optical and polarization vortices using axially-symmetric polarizer (ASP). In the present presentation, we report the experimental study on the Fresnel diffraction characteristics of the vortices generated by ASP. The diffraction pattern of the optical vortex has a dark core whose diameter is not scaled by the beam diameter. This behavior is described by the numerical simulation for a point-like vortex at ASP. We also studied the polarization change of a radially polarized light from ASP owing to the diffraction. This change can be explained by the decomposition of the radially polarized light into a plane wave and a point-like optical vortex which are respectively circularly-polarized with opposite handedness.
  • Takashige Omatsu, Keisuke Chujo, Katsuhiko Miyamoto, Masahito Okida, Kazuki Nakamura, Nobuyuki Aoki, Ryuji Morita
    OPTICS EXPRESS 18 17 17967 - 17973 2010年08月 [査読有り][通常論文]
     
    Microneedle fabrication on a metal surface based on laser ablation using twisted light with spin was demonstrated, for the first time. The resulting needle showed a height of at least 10 mu m above the target surface and a tip diameter of less than 0.3 mu m. We also demonstrated the fabrication of a two-dimensional 5 x 6 microneedle array. The needles were uniformly well shaped with an average length and tip diameter of about 10 and 0.5 mu m, respectively. (C) 2010 Optical Society of America
  • Junichi Hamazaki, Ryuji Morita, Keisuke Chujo, Yusuke Kobayashi, Satoshi Tanda, Takashige Omatsu
    OPTICS EXPRESS 18 3 2144 - 2151 2010年02月 [査読有り][通常論文]
     
    Laser ablation of Ta plates using nanosecond optical vortex pulses was carried out, for the first time. It was suggested that owing to orbital angular momentum of optical vortex, clearer and smoother processed surfaces were obtained with less ablation threshold fluence, in comparison with the ablation by a nonvortex annular beam modified from a spatially Gaussian beam. (C) 2010 Optical Society of America
  • Tokizane Y, Shimatake K, Toda Y, Oka K, Tsubota M, Tanda S, Morita R
    Optics express 17 26 24198 - 24207 26 2009年12月 [査読有り][通常論文]
     
    We evaluate the quasi-one-dimensional (1D) electron dynamics in a NbSe3 ring crystal using polarization vortex pulses with various azimuthal distributions. The single particle relaxation component reveals a large anisotropy on the crystal, indicating that the electrons in the ring maintain their 1D character. The results also suggest that the polarization vortex evaluates the global polarization property of the closed-loop electron that plays an important role in the quantum correlation phenomena such as the Aharonov-Bohm effect.
  • Yu Tokizane, Kazuhiko Oka, Ryuji Morita
    OPTICS EXPRESS 17 17 14517 - 14525 2009年08月 [査読有り][通常論文]
     
    A new achromatic method to generate the optical vortex was proposed and supercontinuum optical vortex generation ranging similar to 500 to similar to 800 nm was experimentally demonstrated without spatial nor topological-charge dispersions. In addition, polarization evolution in our system using Jones vectors and matrices was discussed and the condition of the polarizer to transfer polarizations was elucidated. This method is useful for the application to time-resolved nonlinear spectroscopy utilizing ultrabroadband optical vortex pulses in topological materials such as ring-shaped crystals or annular materials. (C) 2009 Optical Society of America
  • Yasunori Toda, Koshi Nagaoka, Katsuhiro Shimatake, Ryuji Morita
    ELECTRICAL ENGINEERING IN JAPAN 167 4 39 - 46 2009年06月 [査読有り][通常論文]
     
    Topology has become one of the key concepts allowing one to understand the intrinsic, qualitative properties of phenomena throughout various scientific fields. To date, this concept has been extended to the field of material science and technology. On the other hand, we can now utilize the spatially controlled light defined by the topology (so-called "optical vortices") in order to characterize the topological properties of materials. In particular, optical vortices in femtosecond pulses will be invaluable for advanced topological spectroscopy. In this work, the authors created femtosecond optical vortices using a spatial light modulator. Their spatiotemporal properties were evaluated using interferogram and correlation measurements. 0 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(4): 39-46, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20791
  • Junichi Hamazaki, Akira Kawamoto, Ryuji Morita, Takashige Omatsu
    OPTICS EXPRESS 16 14 10762 - 10768 2008年07月 [査読有り][通常論文]
     
    We produced a high power radially-polarized output directly from a diode-pumped Nd:YVO4 bounce amplifier, using an autocloned photonic crystal mirror as an output coupler, with a simple cavity configuration. The radially-polarized output power of similar to 6 W was achieved, and a corresponding slope efficiency was estimated to be similar to 17 %. The output was characterized to be an ideal radially-polarized beam from its polarization distribution profiles. The output mode was not an eigenmode in the resonator. We discussed and clarified intra-cavity mode dynamics in terms of polarization distribution in the wavefront. (C) 2008 Optical Society of America.
  • Hamazaki J, Mineta Y, Oka K, Morita R
    Optics express 14 8382 - 8392 18 2006年09月 [査読有り][通常論文]
  • Shinki Nakamura, Naoya Takasawa, Yahei Koyamada, Hiroyasu Sone, X. U. Lin, Ryuji Morita, Mikio Yamashita
    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 44 10 7453 - 7459 2005年10月11日 [査読有り][通常論文]
     
    Experimental results of nonlinear propagation with the induced-phase modulation (IPM) effect of two-color 120 fs laser pulses with three different initial delays in a silica fiber were analyzed with finite-difference time domain (FDTD) calculations, including self-phase modulation (SPM), IPM, and degenerate four-wave mixing (DFWM) in the fused-silica fiber. Initial delay dependence by the FDTD qualitatively agrees with the previous experimental results. An ultrabroad spectrum induced by IPM mostly agrees with the previous experimental results that had the optimum initial delay. A Fourier transform of this spectrum yields a 4 fs optical pulse, which agrees with the previous experimental results. The spectral phases of two different pulses with three different initial delays are connected continuously. The IPM spectral phase obtained by the extended FDTD shows that the DFWM occurs. To the best of our knowledge, this is the first observation of DFWM with IPM by the FDTD simulation. © 2005 The Japan Society of Applied Physics.
  • S Nakamura, N Takasawa, Y Koyamada, H Sone, L Xu, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 10 7453 - 7459 2005年10月 [査読有り][通常論文]
     
    Experimental results of nonlinear propagation with the induced-phase modulation (IPM) effect of two-color 120 fs laser pulses with three different initial delays in a silica fiber were analyzed with finite-difference time domain (FDTD) calculations, including self-phase modulation (SPM), IPM, and degenerate four-wave mixing (DFWM) in the fused-silica fiber. Initial delay dependence by the FDTD qualitatively agrees with the previous experimental results. An ultrabroad spectrum induced by IPM mostly agrees with the previous experimental results that had the optimum initial delay. A Fourier transform of this spectrum yields a 4 fs optical pulse, which agrees with the previous experimental results. The spectral phases of two different pulses with three different initial delays are connected continuously. The IPM spectral phase obtained by the extended FDTD shows that the DFWM occurs. To the best of our knowledge, this is the first observation of DFWM with IPM by the FDTD simulation.
  • YQ Deng, ZB Wu, L Chai, CY Wang, K Yamane, R Morita, M Yamashita, ZG Zhang
    OPTICS EXPRESS 13 6 2120 - 2126 2005年03月 [査読無し][通常論文]
     
    We introduce a novel method for retrieving the phase from a spectral shearing interferogram, based on wavelet-transform technique. We demonstrate with both theoretical and experimental data that this technique provides an alternative and reliable technique for phase retrieval, particularly for highly structured pulse spectra. (C) 2005 Optical Society of America.
  • Adachi M., Yamane K., Morita R., Yamashita M.: "Sub-5-fs pulse compression of laser output using photonic crystal fiber with short zero-dispersion wavelength", Jpn. J. Appl. Phys., 44: L1423-L1425 (2005)*
    2005年 [査読無し][通常論文]
  • M Adachi, K Yamane, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 46-49 L1423 - L1425 2005年 [査読無し][通常論文]
     
    Output pulses from a photonic crystal fiber (PCF) with a zero-dispersion wavelength (ZDW: 853 nm) were compressed to 5.8 fs by feedback spectral-phase compensation. Furthermore, for another PCF with a shorter ZDW (744 nm), whose output spectral-phase measurement and pulse compression are generally thought to be difficult because of coherence degradation between pulses, we measured successfully their phases in the entire spectral region (480 to 1000 nm) by a suitable selection of input pulse and fiber parameters. The pulse compression experiment using an improved feedback system showed that in the short-wavelength region, pulses can be compressed to 4.9 fs, whereas in the entire spectral region, pulses cannot be compressed. This is because the visibility of the spectral interferogram in the spectral-phase interferometry for direct electric-field reconstruction (SPIDER) signal in the longer-wavelength region corresponding to the phase-sensitive soliton-breaking-up region is degraded by large phase modulation using a spatial light modulator.
  • Ryuji Morita, Muneyuki Adachi, Mikio Yamashita
    Conference on Lasers and Electro-Optics Europe - Technical Digest 2005年 [査読有り][通常論文]
  • R. Morita, K. Yamane, M. Adachi, M. Yamashita
    IQEC, International Quantum Electronics Conference Proceedings 2005 544 - 545 2005年 [査読有り][通常論文]
     
    Nonlinear optical phenomena dominating spectral broadening and spectral phase behavior of pulses propagated in gas-filled or microstructure fibers for compression up to few- to mono-cycle region were discussed from the standpoint of time-frequency characteristics.
  • M Adachi, K Yamane, R Morita, M Yamashita
    ULTRAFAST PHENOMENA XIV 79 49 - 51 2005年 [査読有り][通常論文]
     
    A feedback system that combined modified-SPIDER and 4-f active-chirp compensation enabled us to compress photonic-crystal-fiber and tapered-fiber outputs to 6.6 and 8.4 fs, respectively. Compressed-pulse results well agree with fringe-resolved autocorrelation measurement ones.
  • K Yamane, T Kito, R Morita, M Yamashita
    ULTRAFAST PHENOMENA XIV 79 13 - 15 2005年 [査読無し][通常論文]
     
    We compensated for chirp of ultrabroad-band pulses with an over-one-octave bandwidth (460 - 1060 nm) using a feedback method. Consequently, 2.8-fs, 1.5-cycle transform-limited pulses were generated.
  • Osamu Takeuchi, Masahiro Aoyama, Ryuji Oshima, Yoshitaka Okada, Haruhiro Oigawa, Nobuyuki Sano, Hidemi Shigekawa, Ryuji Morita, Mikio Yamashita
    Applied Physics Letters 85 23 5790  2004年12月06日 [査読有り][通常論文]
  • Osamu Takeuchi Masahiro Aoyama, Ryuji Oshima, Yoshitaka Okada, Haruhiro Oigawa, Nobuyuki Sano, Hidemi Shigekawa, Ryuji Morita, Mikio Yamashita
    Applied Physics Letters 85 15 3268 - 3270 2004年10月11日 [査読無し][通常論文]
     
    Time-resolved tunneling current measurement in the subpicosecond range was realized by ultrashort-pulse laser combined scanning tunneling microscopy, using the shaken-pulse-pair method. A low-temperature-grown GaNxAS 1-x (x=0.36%) sample exhibited two ultrafast transient processes in the time-resolved tunnel current signal, whose lifetimes were determined to be 0.653±0.025 and 55.1±5.0 ps. These values are of the same order of magnitude as those measured in the conventional pump-probe reflectivity measurement. © 2004 American Institute of Physics.
  • K Itoh, Y Toda, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 43 9A 6448 - 6451 2004年09月 [査読有り][通常論文]
     
    By using Raman-induced Kerr-effect spectroscopy, two-pulse excitations with different polarization combinations have been demonstrated for the selective coherent excitation of molecular vibrations in liquid CCl4. Anti correlated selective excitations as well as the suppressions of the two asymmetric vibrational motions were observed in the opposite configuration of polarization between the two-pump pulses. The measurements show that we can manipulate molecular motions by controlling the optical phase of sequential pulses through timing and polarization.
  • M Adachi, K Yamane, R Morita, M Yamashita
    IEEE PHOTONICS TECHNOLOGY LETTERS 16 8 1951 - 1953 2004年08月 [査読無し][通常論文]
     
    Characterization and compensation of the complex spectral phase and the temporal profile of output pulses from a photonic crystal fiber (620-945-nm spectral broadening) were performed using a computer-controlled feedback system that combines a modified spectral-phase interferometry for direct electric-field reconstruction apparatus and only a 4-f chirp compensator having a spatial light modulator. These pulses were adaptively compressed from 12-fs input pulses to 6.8-fs. In addition, the compressed pulse profile showed excellent agreement with results measured independently with fringe-resolved auto-correlation.
  • K Yamane, T Kito, R Morita, M Yamashita
    OPTICS EXPRESS 12 12 2762 - 2773 2004年06月 [査読無し][通常論文]
     
    Using 3.6- and 5.3-fs pulses, we demonstrated theoretically and experimentally that fringe-resolved autocorrelation (FRAC) traces are distorted by bandwidth limitations of the second-harmonic generation (SHG) in 10-mum-thick, type I beta-BaB2O4 for pulses shorter than sub-5 fs. In addition, detailed numerical analysis of the SHG showed that the optimum crystal angle where the FRAC trace distortion becomes minimum is in disagreement not only with the phase-matching angle but also with the angle where the FRAC signal intensity becomes maximum. Furthermore, the apparent pulse duration measured at a nonoptimum angle was confirmed to become shorter than that of its transform-limited pulse, in excellent agreement with the calculated result. (C) 2004 Optical Society of America.
  • Y Toda, T Nakaoka, R Morita, M Yamashita, T Inoue, Y Arakawa
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 2-4 180 - 183 2004年03月 [査読有り][通常論文]
     
    We carried out optical selective excitation of individual self-assembled quantum dots by using phase-modulated pulses. Based on scattered photoluminescence excitation resonances in individual QDs, the excitation pulses modulated in the spectral region allows for addressing individual ground states emission. The photoluminescence spectra including several QDs showed intensity changes according to both the modulation energies and phases. The results also suggested the individual control of selective QDs even in collective excitation. (C) 2003 Elsevier B.V. All rights reserved.
  • M Yamashita, M Hirasawa, N Nakagawa, K Yamamoto, K Oka, R Morita, A Suguro
    JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 21 2 458 - 462 2004年02月 [査読無し][通常論文]
     
    The 530-880-nm continuum pulse with a greatly asymmetric temporal profile over 500 fs and a spectral phase variation over 150 rad, which was generated by induced phase modulation (IPM) as well as self-phase modulation in a conventional fused-silica fiber, was compressed to 7.8 fs by a feedback technique. Fundamental (a center wavelength of 800 nm, a duration of 80 fs, a pulse energy of 64 nJ) and signal pulses (a center wavelength of 670 nm, a duration of 80 fs, a pulse energy of 65 nJ) produced by one common femtosecond source with an optical parametric amplifier were copropagated in the fiber under an optimum delay time between the two pulses. The computer-controlled feedback system that combines a 4-f phase compensator with a spatial light modulator and a modified spectral phase interferometry for a direct electric-field reconstruction, automatically compensated for not only the conventional nonlinear chirp (group-delay dispersion and its higher-order dispersion) but also the frequency-independent group-delay (first-order phase. dispersion), both of which are essential for pulse compression by use of the IPM effect. (C) 2004 Optical Society of America.
  • Takeuchi, O., Aoyama, M., Oshima, R., Okada, Y., Oigawa, H., Sano, N., Morita, R., Yamashita, M., Shigekawa, H.: "Probing subpicosecond dynamics using pulsed laser combined scanning tunneling microscopy", Appl. Phys. Lett., 85: 3268-3270 (2004)*
    2004年 [査読無し][通常論文]
  • Toda, Y., Nakaoka, T., Morita, R., Yamashita, M., Inoue, T., Arakawa, Y.: "Selective excitation of self-assembled quantum dots by using shaped pulse", Physica E, 21: 180-183 (2004)*
    2004年 [査読無し][通常論文]
  • Itoh, K., Toda, Y., Morita, R., Yamashita, M.: "Coherent optical control of molecular motion using polarized sequential pulses", Jpn. J. Appl. Phys., 43: 6448-6451 (2004)*
    2004年 [査読無し][通常論文]
  • K Yamane, ZG Zhang, A Suguro, K Oka, R Morita, M Yamashita
    ULTRAFAST OPTICS IV 95 97 - 102 2004年 [査読有り][通常論文]
     
    We feedback-compensated for chirp of optical pulses with over one-octave bandwidth (495-1090 nm) generated by self-phase modulation in a single-argon-filled hollow fiber, and generated 3.4-fs, 1.56 optical-cycle pulses.
  • Ryuji Morita, Keisaku Yamane, Mikio Yamashita
    OSA Trends in Optics and Photonics Series 96 A 793 - 795 2004年01月01日 [査読無し][通常論文]
     
    Time-frequency analysis of monocycle-region optical pulses was performed using the Wigner distribution function. The difference between the normalized Wigner distribution functions for a measured pulse and its Fourier-transform-limited pulse provides detailed information of their deviations. © 2003 Optical Society of America.
  • Muneyuki Adachi, Keisaku Yamane, Ryuji Morita, Mikio Yamashita
    OSA Trends in Optics and Photonics Series 96 A 783 - 785 2004年01月01日 [査読無し][通常論文]
     
    A computer-contralled feedback system that combined modified-SPIDER and a 4-f active chirp compensator enabled us to compress photonic-crystal-fiber output pulses to 6.8 fs. Furthermore, the compressed-pulse profile showed the excellent agreement with fringe-resolved autocorrelation measurement. © 2003 Optical Society of America.
  • K Yamane, ZG Zhang, K Oka, R Morita, M Yamashita, A Suguro
    OPTICS LETTERS 28 22 2258 - 2260 2003年11月 [査読無し][通常論文]
     
    We, compensated for chirp of optical pulses with an over-one-octave bandwidth (495,71090 run; center wavelength of 655.4 nm) produced by self-phase modulation in a single argon-filled hollow fiber and generated 3.4-fs, 1.56 optical-cycle pulses ( 00 nJ, 1-kHz repetition rate). This was achieved with a feedback system combined with only one 4-f phase compensator with a spatial light modulator and a significantly improved phase characterizer based on modified spectral phase interferometry for direct electric-field reconstruction. To the best of our knowledge, this is the shortest pulse in the visible-to-infrared region. (C) 2003 Optical Society of America.
  • DN Futaba, R Morita, M Yamashita, S Tomiyama, H Shigekawa
    APPLIED PHYSICS LETTERS 83 12 2333 - 2335 2003年09月 [査読有り][通常論文]
     
    We performed an experimental study of silicon adatom desorption from the Si(111)-7x7 surface using femtosecond laser pulse pair excitation with 80 fs pulse duration, 800 nm center wavelength, 300 mW average power, and a 100 MHz repetition rate. Using scanning tunneling microscopy, we directly recorded the desorption characteristics at each delay setting for each of the four adatom binding sites. The study revealed a preferential dependence between the delay time and the adatom sites within a 66.6-1000 fs delay range. (C) 2003 American Institute of Physics.
  • Y Toda, T Matsubara, R Morita, M Yamashita, K Hoshino, T Someya, Y Arakawa
    APPLIED PHYSICS LETTERS 82 26 4714 - 4716 2003年06月 [査読有り][通常論文]
     
    Optical nonlinearity in the yellow luminescence (YL) band of GaN was investigated using thick bulk samples. Transient pump-probe measurements revealed strong transmission changes due to two-photon absorption (TPA) even at the middle of the YL band. The TPA coefficient evaluated reaches similar to5 cm/GW at about 1.3 eV, which was as large as the mid-gap resonance. The TPA spectrum clearly showed that the observed large nonlinearity originated from the YL band. On the basis of efficient TPA in the YL band, relaxation processes in the multiphoton-induced photoluminescence excitation spectrum were also investigated. (C) 2003 American Institute of Physics.
  • NAKAMARU Shinki, KOYAMADA Yahei, KARASAWA Naoki, SONE Hiroyasu, MORITA Ryuji, YAMASHITA Mikio
    IEICE transactions on communications 86 3 449 - 458 一般社団法人電子情報通信学会 2003年03月 [査読無し][通常論文]
     
    We have extended the finite-difference time-domain (FDTD) solution of Maxwell's equations to nonlinear propagation in a silica fiber. The combination of linear polarization, including all exact Sellmeier-fitting values, and nonlinear polarization, involving the Raman response function, in the FDTD method is novel. We have compared the extended FDTD method with the previous solution of the generalized nonlinear Sehrodinger equation by the split-step Fourier method with a slowly varying-envelope approximation, and experimental results. To the best of our knowledge, this is the first compariso...
  • XJ Fang, N Karasawa, R Morita, RS Windeler, M Yamashita
    IEEE PHOTONICS TECHNOLOGY LETTERS 15 2 233 - 235 2003年02月 [査読無し][通常論文]
     
    The evolution of spectral and temporal profiles of 4.5 optical-cycle pulses propagating near zero-dispersion wavelength (ZDW) in a photonic crystal-fiber is investigated experimentally and theoretically beyond the slowly varying-envelope approximation. The excellent agreement between the experimental and theoretical results suggests that the observed gap in the spectral profile, the most distinctive feature, originates from the self-steepening effect. This effect intensifies the. spectral, component shorter than the ZDW with the decay of higher order solitons and consequently induces the intrapulse four-wave mixing (FWM). As a result, the anti-Stokes and Stokes components,produced by the FWM-enables us to generate a supercont inuum 60 In 486 to 1020 nm.
  • Futaba, D. N., Morita, R., Yamashita, M., Tomiyama, S., Shigekawa, H.: "Site-selective silicon adatom desorption using femtosecond laser pulse pairs and scanning tunneling microscopy", Appl. Phys. Lett., 83: 2333-2335 (2003)*
    2003年 [査読無し][通常論文]
  • Adachi, M., Hirasawa, M., Suguro, A., Karasawa, N., Kobayashi, S., Morita, R., Yamashita, M.: "Spectral-phase characterization and adapted compensation of strongly chirped pulses from a tapered fiber", Jpn. J. Appl. Phys., 42: L24-L26 (2003)*
    2003年 [査読無し][通常論文]
  • Toda, Y., Matsubara, T., Morita, R., Yamashita, M., Hoshino, K., Someya, T., Arakawa, T.: "Two-photon absorption and multiphoton-induced photoluminescence of bulk GaN excited below the middle of the band gap", Appl. Phys. Lett., 82: 4714-4716 (2003)*
    2003年 [査読無し][通常論文]
  • Ryuji Morita, Hayato Takenaka, Keisaku Yamane, Mikio Yamashita
    Conference on Lasers and Electro-Optics Europe - Technical Digest 455  2003年 [査読有り][通常論文]
     
    In this paper, we analyze temporal and spectral properties of sub-4 fs optical pulses with over-one-octave bandwidth using Wigner distribution function (WDF). The analytic results suggested that WDF enables us to intuitively and usefully obtain more information about the deviation from the perfect Fourier transform limited FTL pulse than other representations for monocycle-like pulse generation. © 2003 IEEE.
  • Y. Toda, T. Matsubara, R. Morita, K. Hoshino, T. Someya, Y. Arakawa
    Physica Status Solidi C: Conferences 7 2627 - 2630 2003年 [査読有り][通常論文]
     
    Transient transmission changes in the yellow luminescence (YL) band of GaN were investigated using excitation far smaller than the bandgap. At lower excitation power, time-resolved measurements revealed efficient transmission changes due to two-photon absorption (TPA), whose spectrum clearly indicates the contribution of the YL band. Upon increasing the excitation power, the transient signal showed an additional offset signal. The excitation power dependences of the offset suggested a two-step absorption process in conjunction with TPA in the YL band. The excitation energy dependence also supported this conclusion. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.
  • Fang, X, M Hirasawa, RS Windeler, R Morita, M Yamashita
    ULTRAFAST PHENOMENA XIII 71 238 - 240 2003年 [査読有り][通常論文]
     
    The evolution of spectra and temporal profiles of 4.5-optical-cycle pulses propagating near zero dispersion wavelength (ZDW) in a photonic-crystal fiber (PCF) is clarified experimentally and theoretically by indicating that the self-steepening effect inducing the intrapulse four-wave mixing (FWM) is essential. This effect intensifies the spectral component shorter than the ZDW with the decay of higher-order solitons and consequently induces the intrapulse FWM. As a result, the anti-Stokes and Stokes components produced by the FWM enables us to generate a supercontinuum (SC) from 480 to 1020 nm.
  • M Adachi, M Hirasawa, A Suguro, N Karasawa, S Kobayashi, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 42 1A-B L24 - L26 2003年01月 [査読有り][通常論文]
     
    A computer-controlled feedback system that combined a modified spectral-phase interferometer as a direct electric-field reconstruction apparatus and a 4-f pulse shaper with a spatial phase modulator as a programmable chirp compensator was developed. The system enabled us to successfully characterize the complex spectral phase and temporal intensity profile of a weak peak-intensity pulse from a tapered fiber with a high sensitivity comparable to that of the conventional interferometric autocorrelator. In addition, we were able to compress for the first time 185 fs fiber input pulses to 16 fs with subpulses originating from the beat between two splitting-spectral components of the fiber output.
  • Y Toda, T Matsubara, R Morita, K Hoshino, T Someya, Y Arakawa
    5TH INTERNATIONAL CONFERENCE ON NITRIDE SEMICONDUCTORS (ICNS-5), PROCEEDINGS 0 7 2627 - 2630 2003年 [査読有り][通常論文]
     
    Transient transmission changes in the yellow luminescence (YL) band of GaN were investigated using excitation far smaller than the bandgap. At lower excitation power, time-resolved measurements revealed efficient transmission changes due to two-photon absorption (TPA), whose spectrum clearly indicates the contribution of the YL band. Upon increasing the excitation power, the transient signal showed an additional offset signal. The excitation power dependences of the offset suggested a two-step absorption process in conjunction with TPA in the YL band. The excitation energy dependence also supported this conclusion. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • R Morita, M Hirasawa, N Karasawa, S Kusaka, N Nakagawa, K Yamane, LM Li, A Suguro, M Yamashita
    MEASUREMENT SCIENCE AND TECHNOLOGY 13 11 1710 - 1720 2002年11月 [査読無し][通常論文]
     
    Ultrabroadband optical pulses generated through self-phase and induced-phase modulation effects and ultrashort optical pulses whose phases were compensated for using a 4f pulse shaper with a spatial phase modulator were generated. Interferometric autocorrelation, frequency-resolved optical gating and spectral phase interferometry for direct electric-field reconstruction (SPIDER) measurements were made to characterize these pulses, and the results were compared. The generation of 5.0 fs (2.4 cycle) or shorter optical pulses was confirmed. For much shorter pulses, below-two-cycle or monocycle optical pulses, single-shot characterization excluding the errors due to the pulse-to-pulse fluctuation is essential. The sensitivity of SPIDER, which is the most advantageous characterization technique apart from its low sensitivity, was improved by a factor of about a hundred (similar to 1 nJ/THz-bandwidth). Instead of a chirped reference pulse split from the pulse to be characterized, a powerful external pulse from a Ti:sapphire laser amplifier as a highly intensive chirped pulse was employed. By use of this modified SPIDER, the characterization of an over-one-octave ultrabroadband optical pulse was performed. This modified-SPIDER method is the most promising for characterization of monocycle optical pulses.
  • S Yoshida, O Takeuchi, K Hata, R Morita, M Yamashita, H Shigekawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 41 7B 5017 - 5020 2002年07月 [査読無し][通常論文]
     
    The dynamics of a phase defect (P-defect) on the Si(100) surface was studied for the first time by scanning tunneling microscopy in pseudo-real time below 10K, using the repeated-line-scan technique in which single line scans are repeated on the same path along a dimer row. In addition to the pair creation and annihilation of the P-defect, the effect of a step on the motion of the P-defect was clearly demonstrated. Since the local barrier height for the migration of the P-defect depends on the local environment such as strain and electronic structure due to the existence of defects or dopants, the obtained results also indicate that analysis of the P-defect is promising for local probing of the Si(100) surface.
  • O Takeuchi, R Morita, M Yamashita, H Shigekawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 7B 4994 - 4997 2002年07月 [査読無し][通常論文]
     
    A promising design for achieving the ultimate spatial and temporal resolution is proposed. With modulation of the time delay between two femtosecond laser pulses repeatedly illuminating a scanning tunneling microscope junction, the induced component of the tunneling current is detected as a function of the delay time. With this method, a high signal-to-noise ratio, stable measurement free from fluctuation of laser intensity, and removal of the thermal expansion effect can be achieved. Using the photovoltage effect of GaAs, the high performance of the newly developed system is demonstrated in the femtosecond range.
  • M Shibata, M Hirasawa, N Nakagawa, R Morita, A Suguro, H Shigekawa, M Yamashita
    APPLIED PHYSICS B-LASERS AND OPTICS 74 S291 - S294 2002年06月 [査読無し][通常論文]
     
    Shibata, M., Hirasawa, M., Nakagawa, N., Morita, R., Suguro, A., Shigekawa, H., Yamashita, M.: "Experimental demonstration of phase-dispersion compensation for ultra-broadband femtosecond optical pulses generated by induced-phase modulation" Appl. Phys. B 74: S225-S229*
  • M Hirasawa, N Nakagawa, K Yamamoto, R Morita, H Shigekawa, M Yamashita
    APPLIED PHYSICS B-LASERS AND OPTICS 74 S225 - S229 2002年06月 [査読無し][通常論文]
     
    Hirasawa, M., Nakagawa, N., Yamamoto, K., Morita, R., Shigekawa, H., Yamashita, M.: "Sensitivity improvement of spectral phase interferometry for direct electric-field reconstruction for the characterization of low-intensity femtosecond pulses", Appl. Phys. B 74: S291-S294 (2002)*
  • S Nakamura, Y Koyamada, N Yoshida, N Karasawa, H Sone, M Ohtani, Y Mizuta, R Morita, H Shigekawa, M Yamashita
    IEEE PHOTONICS TECHNOLOGY LETTERS 14 4 480 - 482 2002年04月 [査読無し][通常論文]
     
    In order to both experimentally and numerically investigate nonlinear femtosecond ultrabroadband-pulse propagation in a silica fiber, we have extended the finite-difference time-domain (FDTD) calculation of Maxwell's equations with nonlinear terms to that including all exact Sellmeier-fitting values. We have compared results of this extended FDTD method with experimental results, as well as with the solution of the generalized nonlinear Schrodinger equation by the split-step Fourier method with a slowly varying-envelope approximation. To the best of our knowledge, this is the first comparison between FDTD calculation and experimental results for nonlinear propagation of a very short (12 fs) laser pulse in a silica fiber.
  • S Nakamura, LM Li, N Karasawa, R Morita, H Shigekawa, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 3A 1369 - 1373 2002年03月 [査読無し][通常論文]
     
    An active chirp compensator consisting of a prism pair and a spatial-phase-modulating pulse shaper enables us to accurately measure the third-order dispersion (TOD) dependence of the interferometric autocorrelation trace while keeping the optimum group-delay dispersion constant. As a result, it is shown that even a small change in TOD (+60fs(3) and -100fs(3)) greatly affects the temporal pulse profile in the sub-8-fs region, and 92-fs pulses at a 75-MHz repetition rate from a laser-oscillator glass-fiber system is transform-limitedly compressed to 7.1 fs.
  • N Karasawa, LM Li, A Suguro, H Shigekawa, R Morita, M Yamashita
    JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 18 11 1742 - 1746 2001年11月 [査読無し][通常論文]
     
    We experimentally demonstrate the generation of 5.0-fs optical pulses (2.5 muJ, 1-kHz repetition rate), using only a spatial light modulator for phase compensation. Pulse compression of the broadband pulse (500-1000 nm) from an argon-filled capillary fiber is achieved with a liquid-crystal spatial light modulator without any prechirp compensation. The output pulse width is found to be 4.1 is by a fringe-resolved autocorrelator fitted with a transform-limited pulse and to be 5.0 fs by second-harmonic generation frequency-resolved optical gating with marginal correction. It is to our knowledge the shortest pulse ever generated by use of only a spatial light modulator for phase compensation. (C) 2001 Optical Society of America.
  • N Karasawa, R Morita, H Shigekawa, M Yamashita
    OPTICS COMMUNICATIONS 197 4-6 475 - 480 2001年10月 [査読無し][通常論文]
     
    Karasawa, N., Morita, R., Shigekawa, H. and Yamashita, M.: ``Characteristics of the Oscillatory Spectrum Due to Only Induced-Phase Modulation in an Argon-Filled Hollow Waveguide Accompanied with Intense Self-Phase Modulation", Opt. Commun., 197: 475-480 (2001)*
  • R Morita, M Yamashita, A Suguro, H Shigekawa
    OPTICS COMMUNICATIONS 197 1-3 73 - 81 2001年09月 [査読無し][通常論文]
     
    Morita, R. Yamashita, M. Suguro A. and Shigekawa, H.:``Femtosecond-Time-Resolved Highly-Selective Molecular-Vibration Excitation Using a Novel Vibrationally-Synchronized Pumping Technique with Frequency-Difference Resonance", Opt. Commun., 197: 73-81 (2001)*
  • LM Li, S Kusaka, N Karasawa, R Morita, H Shigekawa, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 40 7A L684 - L687 2001年07月 [査読無し][通常論文]
     
    The amplitude and phase of 5.0 fs optical pulses with an ultrabroad bandwidth from 480 to 835 nm were rapidly characterized by the spectral phase interferometry for direct electric-field reconstruction (SPIDER) technique. To our knowledge, this is the shortest pulse ever measured by the SPIDER technique, To solve the problems of dispersion, bandwidth, sensitivity and wavelength resolution, which are essential for few-optical-cycle pulse characterization, we developed a SPIDER apparatus equipped with ultrabroad-band (450-850 nm) beam splitters, a thin (25 mum) beta -BaB2O4 crystal, a 0.5 in spectrometer capable of the automatic and fast control of two gratings (1200 and 150 lines/mm) and a highly sensitive intensified charge-coupled device.
  • N Karasawa, S Nakamura, N Nakagawa, M Shibata, R Morita, H Shigekawa, M Yamashita
    IEEE JOURNAL OF QUANTUM ELECTRONICS 37 3 398 - 404 2001年03月 [査読無し][通常論文]
     
    Wave-propagation equations, including effectively the second derivative in time under the condition of a small difference between the group and phase velocities and the first derivative in position xi in the group velocity coordinate, are derived based on the slowly evolving wave approximation. These can describe ultrabroadband optical pulse propagation with not only self-phase modulation (SPM), but also induced-phase modulation (IPM) in the monocycle regime in a fiber. It is shown that linear dispersion effects can be rigorously included in the numerical calculations, Calculations including SPM in a single-mode fused-silica fiber with the Raman effect are performed and compared with experimental results. Also, calculations including IPM in the fused-silica fiber are compared with experimental results, The effects of each term in the calculations on spectra are analyzed and it is shown that inclusion of the Raman effect and the dispersion of the effective core area is important for obtaining better agreement with experiments, It is shown that inclusion of more than third-order dispersion terms is necessary for calculations of monocycle pulse propagation.
  • Oyama, S., Miyake, K., Yasuda, S., Takeuchi, O., Sumaoka, J., Komiyama, M.,Futaba, D. N., Morita, R., Yamashita M. and Shigakawa, H.: ``Interactive Force Between Cyclodextrin Inclusion Complexes Studied by Atomic Force Microscopy",Jpn. J. Appl・・・
    2001年 [査読無し][通常論文]
     
    Oyama, S., Miyake, K., Yasuda, S., Takeuchi, O., Sumaoka, J., Komiyama, M.,Futaba, D. N., Morita, R., Yamashita M. and Shigakawa, H.: ``Interactive Force Between Cyclodextrin Inclusion Complexes Studied by Atomic Force Microscopy",Jpn. J. Appl. Phys., 40: 4419-4422 (2001)*
  • Hirasawa, M., Nakagawa, N., Shibata, M., Morita, R., Shigekawa H. and Yamashita, M.:``Experimental Studies on Phase Characteristics of Ultrabroad-band Pulses Generated by Induced-Phase Modulation in a Fused-Silica Fiber", Technical Digest of Con・・・
    2001年 [査読無し][通常論文]
     
    Hirasawa, M., Nakagawa, N., Shibata, M., Morita, R., Shigekawa H. and Yamashita, M.:``Experimental Studies on Phase Characteristics of Ultrabroad-band Pulses Generated by Induced-Phase Modulation in a Fused-Silica Fiber", Technical Digest of Conference on Lasers and Electro-Optics (CLEO): 270-271 (2001)*
  • Miyake, K., Okawa, S., Takeuchi, O., Futaba, D. N., Morita, R., Yamashita, M. and Shigakawa, H.: ``Characteristic Structure of the Si(111)-7x7 Surface Step Studied by Scanning Tunneling Microscopy", J. Vac. Sci. Technol. A, 19: 1549-1552 (2001)*
    2001年 [査読無し][通常論文]
  • Oyama Shigeo, Miyake Koji, Yasuda Satoshi, Takeuchi Osamu, Sumaoka Jun, Komiyama Makoto, Futaba Don Norimi, Morita Ryuji, Yamashita Mikio, Shigekawa Hidemi
    Japanese Journal of Applied Physics 40 6 4419 - 4422 公益社団法人 応用物理学会 2001年 
    Change in the intermolecular interaction between cyclodextrins (CyDs) with guest materials was observed by measuring the adhesion force using atomic force microscopy (AFM) in air. The observed adhesion force with water as the guest material is weaker for α-CyD (composed of 6 glucose) than β-CyD (7 glucose), contrary to the fact that α-CyD is more hydrophilic than β-CyD, indicating that the intrinsic interaction of molecules could be obtained separately from the meniscus force even in air. In addition, the adhesion force depends on the type of guest molecules (H2O, para-nitrophenol, and triethylendiamine) for α-CyDs, but not for β-CyDs. The observed change was explained well by the change in the dipole moment induced by the structural deformation due to the guest materials.
  • LM Li, S Kusaka, N Karasawa, R Morita, M Yamashita, H Shigekawa
    CLEO(R)/PACIFIC RIM 2001, VOL II, TECHNICAL DIGEST 726 - 727 2001年 [査読有り][通常論文]
     
    The amplitude and phase of 5.0-fs optical pulses were characterized by a spectral phase interferometry for direct electric-field reconstruction (SPIDER) technique. This is the shortest pulse ever measured by the SPIDER technique to our knowledge.
  • L Xu, N Nakagawa, R Morita, M Yamashita
    ULTRAFAST PHENOMENA XII 66 68 - 70 2001年 [査読有り][通常論文]
     
    We experimentally demonstrate the first programmable optical pulse compression to 6 fs using a prism-pair-formed pulse shaper with a spatial light modulator. This method manifests the potential to compress pulses to the one-cycle regime.
  • S Nakamura, L Li, N Karasawa, R Morita, H Shigekawa, M Yamashita
    ULTRAFAST PHENOMENA XII 66 56 - 58 2001年 [査読有り][通常論文]
     
    92-fs, 75-MHz-repetitive pulses from a simple laser-oscillator glass-fiber system were compressed to 7.1-fs transform-limitedly by a chirp compensator consisting of a prism-pair and a spatial-phase-modulating pulse shaper that in-situ-adjusts independently and accurately any order dispersions.
  • L. Xu, Liming Li, N. Nakagawa, R. Morita, M. Yamashita
    IEEE Photonics Technology Letters 12 11 1540 - 1542 2000年11月 [査読無し][通常論文]
     
    We present a grating-pair-formed pulse shaper with a spatial light modulator (SLM) for programmable chirp compensation by applying voltages on the SLM. When linear and non-linear chirp are optimally compensated for, corresponding to the quadratic, cubic, and quartic phases of -400 fs 2, 1100 fs 3, and 2000 fs 4 at the center wavelength 780 nm on the SLM, a stronger chirped white light continuum (WLC) pulse with a spectral bandwidth of 570-970 nm is compressed to the sub-6-fs regime.
  • YAMAOKA Yoshihisa, MORITA Ryuji, YAMASHITA Mikio
    Optical review 7 6 489 - 494 2000年11月 [査読無し][通常論文]
     
    We measure the femtosecond time-dependent, third-order nonlinear optical response for 4-(N,N-diethylamino)-beta -nitrostyrene (DEANST) dissolved in N, N-dimethylformamide (DMF) from 0.1 to 1.4 M concentrations in the nonresonant region using time-resolved degenerate four-wave mixing (DFWM) spectroscopy. It is found that the DFWM signal profile with delayed responses depends on the concentration. This concentration dependence is determined to be mainly due to the group-velocity dispersion effect of the DEANST solution at the high concentration and the nonlinear response of the DMF solvent at the low concentration, but not due to the change in third-order nonlinear response of DEANST itself.
  • L Xu, LM Li, N Nakagawa, R Morita, M Yamashita
    IEEE PHOTONICS TECHNOLOGY LETTERS 12 11 1540 - 1542 2000年11月 [査読有り][通常論文]
     
    We present a grating-pair-formed pulse shaper with a spatial light modulator (SLM) for programmable chirp compensation by applying voltages on the SLM, When linear and nonlinear chirp are optimally compensated for, corresponding to the quadratic, cubic, and quartic phases of -400 fs(2), 1100 fs(3), and 2000 fs(4) at the center wavelength 780 nm on the SLM, a stronger chirped white light continuum (WLC) pulse with a spectral bandwidth of 570-970 nm is compressed to the sub-6-fs regime.
  • H Murakami, R Morita, T Watanabe, K Asai, Honma, I, HS Zhou, M Yamashita, K Ishigure, H Shigekawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 39 10 5838 - 5841 2000年10月 [査読無し][通常論文]
     
    The absorption and electroabsorption (EA) spectra of 1-methyl-1'-octadecyl-2,2'-cyanine perchlorate (S120) Langmuir-Blodgett films were measured. From these results, dispersion of the third-order nonlinear optical susceptibility chi ((3))(-omega; 0, 0, omega) in the range of 1.8 to 2.7 eV was determined. In addition, the linear-polarizability difference Delta alpha and the permanent dipole-moment difference Delta mu between excited and ground states were evaluated. Upon comparison with the results of measurement of the S120 monomer film, it was found that the third-order nonlinear optical susceptibility of the S120 LB film is strongly enhanced by a factor of 1000. It was concluded that this strong enhancement is attributed to the fact that S120 molecules with a short methyne chain that tightly binds two quinoline rings form a rigid J-aggregate with a one-dimensional structure that hardly twists, so as to yield a sharp absorption band with a large transition moment. Finally, we evaluated the average aggregation number of the S120 LB film to be 3-4.
  • Lin Xu, N. Nakagawa, R. Morita, H. Shigekawa, M. Yamashita
    IEEE Journal of Quantum Electronics 36 8 893 - 899 2000年08月 [査読無し][通常論文]
     
    We describe a TF5 prism-pair-formed pulse shaper for programmable pulse chirp compensation. The advantages of this kind of pulse shaper are: 1) very broad bandwidth of transmission: 2) smaller losses and 3) no requirement for a large-size spatial light modulator (SLM) if the input spectrum is very broad. In our experiment, an ultrabroad spectral (500-1000 nm) pulse is produced by launching 1-kHz, 30-fs, 400-μJ pulses at 780 nm into an argon-filled glass capillary fiber at the gas pressure of 2.0 bar. The fiber has an inner diameter of 140 μm and a length of 60 cm. The chirped pulse is first precompressed by a pair of BK7 prisms with a separation length of 65 cm and then directed into the prism-pair-formed pulse-shaping apparatus with a 128-pixel SLM, which provides quadratic and cubic phase compensation. When the quadratic and cubic phases are -330 fs2 and +2000 fs3, respectively, at the wavelength of 760 nm, an ultrashort optical pulse of 6 fs (FWHM) is generated. This is, to the best of our knowledge, the shortest optical pulse ever compressed using the SLM pulse-shaping technique.
  • L Xu, N Nakagawa, R Morita, H Shigekawa, M Yamashita
    IEEE JOURNAL OF QUANTUM ELECTRONICS 36 8 893 - 899 2000年08月 [査読有り][通常論文]
     
    We describe a TF5 prism-pair-formed pulse shaper for programmable pulse chirp compensation. The advantages of this kind of pulse shaper are: 1) very broad bandwidth of transmission; 2) smaller losses; and 3) no requirement for a large-size spatial light modulator (SLM) if the input spectrum is very broad. In our experiment, an ultrabroad spectral (500-1000 nm) pulse is produced by launching 1-kHz, 30-fs, 400-mu J pulses at 780 nm into an argon-filled glass capillary fiber at the gas pressure of 2.0 bar. The fiber has an inner diameter of 140 mu m and a length of 60 cm, The chirped pulse is first precompressed by a pair of BK7 prisms with a separation length of 65 cm and then directed into the prism-pair-formed pulse-shaping apparatus with a 128-pixel SLM, which provides quadratic and cubic phase compensation. When the quadratic and cubic phases are -330 fs(2) and +2000 fs(3), respectively, at the wavelength of 760 nm, an ultrashort optical pulse of 6 fs (FWHM) is generated. This is, to the best of our knowledge, the shortest optical pulse ever compressed using the SLM pulse-shaping technique.
  • T Kaikoh, K Miyake, YJ Li, R Morita, M Yamashita, H Shigekawa
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS 18 4 1469 - 1472 2000年07月 [査読無し][通常論文]
     
    Kaikoh T., Miyake K., Li Y. J., Morita R., Yamashita M., Shigekawa H.:
    "Site preferences of oxygen and boron atoms during dissociative reaction of HBO/sub 2/ molecules onto the Si(111)-7*7 surface",
    Journal of Vacuum Science & Technology, 18: 1469-1472 (2000)*
  • Y Yamaoka, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 39 3A 1170 - 1171 2000年03月 [査読無し][通常論文]
     
    We numerically analyze the group-velocity dispersion (GVD) effect of the nonlinear medium on the femtosecond time-resolved degenerate four-wave mixing (DFWM) signal with the third-order nonlinear delayed response. As a result, we find that material GVD greatly influences not only the magnitude but also the temporal profile of the DFWM signal.
  • N Karasawa, R Morita, H Shigekawa, M Yamashita
    OPTICS LETTERS 25 3 183 - 185 2000年02月 [査読無し][通常論文]
     
    We experimentally demonstrate the generation of intense ultrabroadband optical pulses whose spectrum ranges from 300 to 1000 nm (700-THz bandwidth) with a well-behaved spectral phase and 23-mu J pulse energy by a novel, simple setup utilizing induced phase modulation (IPM) in an argon-filled single-mode hollow waveguide. Fundamental as well as second-harmonic pulses produced by one common femtosecond pulse from a Ti:sapphire laser-amplifier system are copropagated in the hollow waveguide. The effect of the delay time between the two input pulses on the IPM spectral broadening is clarified and confirmed to agree with the theoretical result. It is found that the compressed pulse duration from this pulse is 1.51 fs if its phase is completely compensated for. (C) 2000 Optical Society of America. OCIS codes: 060.4370, 060.7140, 320.5520, 320.5540, 320.7140.
  • R Morita, N Kameya, M Yamashita, A Suguro, H Shigekawa
    NONLINEAR OPTICS: MATERIALS, FUNDAMENTALS, AND APPLICATIONS 46 356 - 358 2000年 [査読無し][通常論文]
     
    Morita R., Kameya N., Yamashita M., Suguro A., Shigekawa H.:
    "Simultaneous coherent multicolor pulse shaping using two-dimensional spatial light amplitude- and phase-modulator for multi-selective wave-packet control",
    Nonlinear Optics: Materials, Fundamentals, and Applications. Technical Digest. 46: 356-358 (2000)
  • Naoki Karasawa, Shinki Nakamura, Ryuji Morita, Hidemi Shigekawa, Mikio Yamashita
    Nonlinear Optics 24 133-138 - 138 2000年 [査読有り][通常論文]
  • Programmable optical pulse compression to sub-5 fs using a spatial light modulator
    Lin Xu, Naoya Nakagawa, Shinki Nakamura, Masato Shibata, Ryuji Morita, Hidemi Shigekawa, Mikio Yamashita
    Conference on Lasers and Electro-Optics CThE6 412-413  2000年 [査読無し][通常論文]
  • Feedback compensation for highly nonlinear-chirped pulses with ultrabroad spectra
    Shinki Nakamura, Kenichiro Matsumoto, Ryuji Morita, Hidemi Shigekawa, Mikio Yamashita
    The 6th International workshop on femtosecond technology, Chiba, Japan, July 14, 1999, paper WC-8 68  1999年07月14日 [査読無し][通常論文]
  • M Yamashita, S Kikuma, Y Yamaoka, H Murakami, R Morita, H Shigekawa
    APPLIED PHYSICS LETTERS 75 1 28 - 30 1999年07月 [査読無し][通常論文]
     
    The femtosecond second hyperpolarizability due to the nonresonant electronic polarization for two intramolecular charge-transfer molecules, 6-propionyl-2-dimethylamino naphthalene and 2-anilinonaphthalene-6-sulfonic acid which possess the great permanent dipole-moment difference between the excited state and the ground state, is obtained from the measurement of the ultrafast change in refractive index using a time-resolved interferometer. It is found that the second hyperpolarizability increases parabolically from 5 x 10(-34) to 4.3 x 10(-32) esu with increasing the dipole-moment difference from 7.7 to 40 D, and this quantitative relationship is well explained by a quantum-mechanical equation describing the electronic second hyperpolarizability of one molecule with the permanent dipole-moment difference. (C) 1999 American Institute of Physics. [S0003-6951(99)02025-2].
  • Murakami Hidetoshi, Morita Ryuji, Yamashita Mikio, Shigekawa Hidemi
    Japanese journal of applied physics. Pt. 1, Regular papers & short notes 38 7A 4056 - 4064 The Japan Society of Applied Physics 1999年07月 [査読無し][通常論文]
     
    The absorption and electroabsorption (EA) spectra for 4-(N, N-diethylamino)-4-nitrostyrene (DEANST)-doped poly(methylmethacrylate) (PMMA) films in the dopant concentration range of 0.1-40 wt% were measured. Dispersion of the third-order nonlinear optical susceptibility X^<(3)> (-ω: 0, 0, ω) at each concentration was determined. In addition, the static polarizability change Δα and the static dipole-moment change Δμ were evaluated. Furthermore, the picosecond emission-decay profiles and the time-resolved emission spectra for 0.1-40 wt% DEANST-doped PMMA films were measured. From the experimen...
  • K Miyake, T Kaikoh, K Hata, R Morita, M Yamashita, H Shigekawa
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS 17 4 1596 - 1601 1999年07月 [査読有り][通常論文]
     
    We have investigated the breakdown process of the 7x7 structure during its transition to the (root 3X root 3)R30 degrees phase induced by HBO2 irradiation. The 7x7 structure was destroyed over the wide area before the nucleation of the (root 3X root 3)R30 degrees phase. Even when the (root 3X root 3)R30 degrees structure nucleated in the disordered area, disordered structure existed between the domains of the 7x7 and (root 3x root 3)R30 degrees structural phases. The observed results are completely different from the (root 3x root 3)R30 degrees formation processes induced by other group III atoms, where (root 3X root 3)R30 degrees phases are formed as adjacent to the 7x7 structural domains. The surface B atom concentration in the 7x7, disordered, and (root 3x root 3)R30 degrees regions were estimated to be about one, three, and six per 7x7 unit cell. The disordered structure remained on the surface even after annealing the sample at 750 and 900 degrees C. And the B concentration in the disordered region did not change. These results indicate that the disordered structure is an intrinsic nature of the B-induced reconstruction, and suggest the existence of the relationship between the B atom concentration and the stability of the 7x7 structure. (C) 1999 American Vacuum Society. [S0734-2101(99)10204-5].
  • T. Yamada, K. Miyake, M. Ishida, K. Hata, R. Morita, M. Yamashita, H. Shigekawa
    Synthetic Metals 103 1-3 2653 - 2654 1999年06月24日 [査読有り][通常論文]
     
    Graphite surfaces treated with NaOH, LaCl3 and CeCl3 aqueous solutions were studied by scanning tunneling microscopy. These metals in the compounds are known to have poor lattice matching with graphite. In the presence of low densities of intercalants, which are not enough to form a stage structure, the existence of large periodic superstructures was confirmed. Since the observed structures could not be interpreted by Moire pattern hypothesis, they might be directly related to the intercalant arrangement. The obtained results directly show the importance of long-range interactions for the understanding of the graphite intercalation compound structures as predicted by theoretical studies.
  • K Miyake, H Oigawa, K Hata, R Morita, M Yamashita, H Shigekawa
    SURFACE SCIENCE 429 1-3 260 - 273 1999年06月 [査読無し][通常論文]
     
    By considering the charge transfer from adatoms to rest atoms, the structure of the dimer and stacking-fault (DS) layers in the Si(111) dimer-adatom-stacking-fault (DAS) structure was analyzed at a subunit level on a quenched surface. In comparison with the modified model of Vanderbilt, corner holes with a completed DS structure in the second layer, completed corner holes, were confirmed to play a key role not only in the mechanism to stabilize the DAS structure, but also in its formation process. The formation of the completed corner hole works as a rate-limiting process for the growth of the DAS structure. This mechanism was shown to be quite consistent with the experimental results obtained using scanning tunneling microscopy on the quenched Si(111) surface. (C) 1999 Elsevier Science B.V. All rights reserved.
  • K Hata, R Morita, M Yamashita, H Shigekawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 6B 3837 - 3840 1999年06月 [査読無し][通常論文]
     
    The dynamical characteristics of the C defect at low temperature (80 K) were studied by sequential scanning tunneling microscopy observations. We found that the: C defect frequently transforms into a another type of defect termed as the C-2(LT) defect. In addition, the reversal C-2(LT) to C defect structural transformation was observed which implies that the C-2(LT) defect is a metastable state of the C defect. The observed structural transformation was completely different from that observed at room temperature. We interpret that structural transformation associated with a change in the phase of the defect is suppressed at low temperatures because it disturbs the ordering of the surrounding buckled dimers.
  • Y Sainoo, T Kimura, R Morita, M Yamashita, K Hata, H Shigekawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 6B 3833 - 3836 1999年06月 [査読無し][通常論文]
     
    The A defects on the Si(100) surface can be classified as A(1), A(2), and A(3) at low temperatures. We carried out scanning tunneling microscopy observations and scanning tunneling spectroscopy measurements at similar to 80 K to study their electronic structures. We found that the AI defect is semiconductive similar to the A defect at room temperature (RT), while the A(2) and A(3) defects exhibited states in the surface band gap at 80 K. On comparing these results with the theoretical models, we concluded that the A(1) defect correspond to the Rebonded vacancy model. The broken vacancy model and the twisted vacancy models are the possible candidates for the A(2) and A(3) defects, respectively.
  • K Hata, T Kimura, Y Sainoo, K Miyake, R Morita, M Yamashita, H Shigekawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 5A 2904 - 2909 1999年05月 [査読無し][通常論文]
     
    At 80 K, not all the: aimers of Si(100) appear buckled in the scanning tunneling microscopy (STM) images but a certain number of the dimers are observed in a symmetric configuration. We report on observations of a two-dimensional spontaneous fluctuation of the symmetric double left right arrow buckled dimer domains at some particular locations. We interpret the spontaneous fluctuation to be induced by the competition of several antiphased c(4 x 2) buckled domains to expand. The fluctuation of domains was interpreted by two mechanisms: a fast switching between buckled dimer domains and symmetric dimers induced by migration of P defects.
  • N Karasawa, R Morita, L Xu, H Shigekawa, M Yamashita
    JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 16 4 662 - 668 1999年04月 [査読無し][通常論文]
     
    Generation of an ultrabroadband optical pulse with a fluent frequency dependency of the phase is important for creating a monocyclelike optical pulse and for shaping multiwavelength optical pulses. A previously proposed method that uses induced phase modulation between a femtosecond fundamental wave omega(1) and its second-harmonic wave omega(2) = 2 omega(1) in a fused-silica fiber is applied to a capillary fiber filled with noble gas. Analytic results of chirps without dispersion but with loss in the fiber are shown, and the optimum conditions relating to a delay time between two pulses and to input peak powers are found for fully covering the spectrum between omega(1) and omega(2). Furthermore, numerical calculations, including dispersion effects of the fundamental and the second-harmonic waves from a Ti:sapphire laser-amplifier system with experimentally realizable parameters, are presented. These calculations show that it is possible to generate an ultrabroadband optical pulse whose spectrum ranges from 300 to 900 THz (330 to 1000 nm) with quasi-linear chirp by this method. (C) 1999 Optical Society of America [S0740-3224(99)01604-5] OCIS codes: 060.4370, 060.7140, 320.5520, 320.5540, 320.7140.
  • L Xu, N Karasawa, N Nakagawa, R Morita, H Shigekawa, M Yamashita
    OPTICS COMMUNICATIONS 162 4-6 256 - 260 1999年04月 [査読有り][通常論文]
     
    An ultra-broad spectrum over the range from 480 to 900 nm is experimentally generated by induced-phase modulation (IPM) of two 120 fs intense optical pulses copropagating in a 3-mm single-mode fused-silica fiber for the first time to our knowledge, The center wavelengths of the two pulses are 640 nm and 795 nm. respectively. The Fourier transform of this spectrum yields a transform limited 4 fs optical pulse. This IPM-induced spectrum broadening method opens the way to monocycle optical pulse generation in the near future, (C) 1999 Elsevier Science B.V, All rights reserved.
  • Morita, R., Yanagisawa, H., Yamashita M. and Oka, K.:"Femtosecond Optical Nonlinearity through a Two-Photon Process in Carotenoid Solutions", Nonlinear Opt., 22: 409-412 (1999)*
    1999年 [査読無し][通常論文]
  • Murakami, H. Morita, R, and Yamashita, M.: "Concentration Dependence Study of the Third-Order Nonlinearity in 4-(N,N-Diethylamino)-β-Nitrostyrene (DEANST) Doped Polymer Films by Use of Electroabsorption Spectroscopy", Nonlinear Opt., 22: 385-388 (1999)*
    1999年 [査読無し][通常論文]
  • Yamada, T., Miyake K., M. Ishida, Hata, K., Morita, R., Yamashita, M., Shigekawa, H.: " Long Range Ordering in the Graphite Intercalation Compounds", Synthetic Metals, 103: 2653-2654 (1999)*
    1999年 [査読無し][通常論文]
  • Yoshihisa Yamaoka, Ryuji Morita, Mikio Yamashita
    Molecular Crystals and Liquid Crystals Science and Technology Section B: Nonlinear Optics 22 1-4 381 - 384 1999年 [査読無し][通常論文]
     
    Yamaoka, Y., Morita, R. and Yamashita, M.: "Group-Velocity Dispersion Effect on the Femtosecond Time-Dependent, Degenerative Four-Wave Mixing Signal near the Absorption Edge of 4-(N,N-diethylamino)-β-Nitrostyrene (DEANST) Solutions", Nonlinear Opt., 22: 381-384 (1999)*
  • H Murakami, R Morita, T Watanabe, K Asai, Honma, I, HS Zhou, M Yamashita, K Ishigure, H Shigekawa
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 327 31 - 35 1999年 [査読無し][通常論文]
     
    Murakami, H., Morita, R., Watanabe, T., Asai K. et al.(外5人): "Third-Order Nonlinear Optical Susceptibility Measurement in 1-Methyl-1'- Octadecyl-2,2'-Cyanine Perchlorate Langmuir-Blodgett Films by Means of Electroabsorption Spectroscopy", Mol. Cryst. & Liq. Cryst., 327:31-35 (1999)*
  • Xu, L. Karasawa, N. Nakagawa, N., Morita, R., Shigekawa H. and Yamashita, M.: "Experimental Generation of an Ultra-Broad Spectrum Based on Induced-Phase Modulation in a Single-Mode Glass Fiber", Opt. Commun., 162: 256-260 (1999)*
    1999年 [査読無し][通常論文]
  • L. Xu, N. Nakagawa, R. Morita, H. Shigekawa, M. Yamashita
    CLEO/Pacific Rim 1999 - Pacific Rim Conference on Lasers and Electro-Optics 3 666 - 667 1999年 [査読有り][通常論文]
     
    The broad optical spectrum with quasi-linear chirp is one of the main prerequisites for short pulse generation because of the Fourier relation. Spectrum broadening of laser pulses by self-phase modulation (SPM) in a single-mode optical fiber is a well-established technique and up to now the shortest optical pulses were generated with this technique. To produce even shorter optical pulses, even broader optical spectra are needed. However, this technique has a problem that optical breakdown occurs owing to photo-ionization at the high energy level. Recently, a monocycle-like optical pulse generation using induced-phase modulation (IPM) in a fiber was proposed. In this paper, we report the first experimental demonstration of the ultra-broad coherent spectrum generation based on IPM of two intense, carrier-phase-locked femtosecond pulses.
  • N. Karasawa, R. Morita, H. Shigekawa, M. Yamashita
    CLEO/Pacific Rim 1999 - Pacific Rim Conference on Lasers and Electro-Optics 3 664 - 665 1999年 [査読有り][通常論文]
     
    Generation of an ultrabroadband optical pulse with a fluent frequency-dependency of the phase is important, for example, for shaping multi-wavelength optical pulses and monocyclization. When two optical pulses, one fundamental, the other generated by second harmonic generation, are co-propagated in a nonlinear waveguide, induced-phase modulation (IPM) between them, as well as self-phase modulation (SPM), can be used to broaden the spectrum of each pulse. Since the second-harmonic wave as well as the fundamental wave are generated from one common femtosecond pulse, the carrier-phase difference between their waves is constant and these can be synthesized constructively after propagation. For a case where a capillary fiber filled with noble gas is used as an almost-dispersionless, nonlinear waveguide, we analysed the optimum delay between two pulses and powers required for covering spectrum between two pulses and it was predicted that the generation of the optical pulses whose spectrum covers from near-ultraviolet to near-infrared was possible. To verify these predictions, experimental studies have been performed.
  • M Yamashita, H Sone, R Morita, H Shigekawa
    IEEE JOURNAL OF QUANTUM ELECTRONICS 34 11 2145 - 2149 1998年11月 [査読無し][通常論文]
     
    Detailed numerical analysis of monocyclical optical pulse generation using induced-phase modulation between two-color carrier-phase-locked femtosecond pulses is presented. For the generation of a short pulse with a quasi-linear chirped white-continuum spectrum, it is found to be important that the large spectral broadening of each input pulse after fiber propagation is as similar as possible and the total spectral intensity of the synthesized wave at the fiber output is as homogenous as possible. As a result, it is shown that a 2.2-fs 1.3-cycle pulse is generated.
  • K Miyake, K Akutsu, T Yamada, K Hata, R Morita, M Yamashita, H Shigekawa
    ULTRAMICROSCOPY 73 1-4 185 - 189 1998年06月 [査読無し][通常論文]
     
    Giant superstructures with 1.71 and 9.1 nm lattice constants were observed by scanning tunneling microscopy (STM) on the surface of highly oriented pyrolytic graphite (HOPG) treated with NaOH solution. These structures were analyzed by the moire pattern hypothesis, For both the structures, the orientation angle mismatch of the giant lattices relative to the original atomic lattice of graphite was observed between the theoretical and experimental values. In addition, for the latter structure, the observed boundaries between the superstructural domain and the normal areas were straight, which is different from the theoretically predicted zigzag shape boundary. These discrepancies suggest the existence of some other mechanism responsible for the giant superstructures appearing in graphite intercalation compound surfaces. (C) 1998 Elsevier Science B.V. All rights reserved.
  • Y Sato, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 36 11 6768 - 6774 1997年11月 [査読無し][通常論文]
     
    We propose a new femtosecond optical pulse compressor using a CS2 liquid-core fiber with negative delayed nonlinear response through induced-phase modulation in a normal-dispersion region. We numerically confirm that, with a 23 kW, 100 fs pump pulse, a 100 fs hyperbolic-secant pulse is compressed to similar to 30 fs by this compressor without any additional external phase compensation. From the comparison of effective nonlinear refractive index between CS2 and silica fibers, it is shown that the efficiency of this compressor is almost the same as that of the conventional silica fiber-grating compressor.
  • Tomoharu Fujiwara, Yukio Kamoshida, Ryuji Morita, Mikio Yamashita
    Journal of Photochemistry and Photobiology B: Biology 41 1-2 114 - 121 1997年11月 [査読有り][通常論文]
     
    Picosecond time-resolved emission behaviors of guanine (G), guanosine (GS) and guanosine 5'-monophosphate (GMP) in neutral-acidic aqueous solutions at room temperature are clarified with a few ps time resolution by use of a frequency-tripled femtosecond pulse laser and a highly sensitive streak camera. Each emission consists of a fast decaying (decay constant τ1, = 4-5 ps at around 335-349 nm peak-wavelengths) and a slow decaying (τ2 = 100-200 ps at around 352-382 nm peak-wavelengths) components, excepting that of the neutral GS and GMP solutions which have only fast decaying components. The fast component is assignable to a monomer fluorescence as compared with the results reported previously in the steady-state fluorescence measurements. The slow component, which increases with a decrease in pH value, is assignable to a fluorescence from the N-7 protonated cationic molecule. From the pH dependence of the temporally separated fluorescence intensity of the cation, the electrolytic dissociation exponents pK are obtained to be 2.6-3.0. Moreover, the fluorescence quantum yields of the cations of G, GS and GMP in aqueous solutions at room temperature are obtained in addition to those of their neutral monomers.
  • T Suemura, M Ohtani, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 36 10A L1307 - L1310 1997年10月 [査読無し][通常論文]
     
    Change in the refractive index at around 630 nm in the femtosecond time region has been measured for the first time for a 75-wt% PbO-doped silica single-mode fiber with a highly sensitive, time-resolved interferometer using a heterodyne pump-probe technique. The result shows that the instantaneous response, nonlinear refractive index is 9.8 times as large as that of a conventional fused-silica fiber. This suggests that the PbO fiber is useful for efficient optical pulse compression and ultrafast optical switching in the visible and near-infrared wavelength region.
  • Y Sato, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 36 4A 2109 - 2115 1997年04月 [査読無し][通常論文]
     
    We investigated time responses of components parallel n(2 parallel to)(t) and perpendicular n(2 perpendicular to)(t) to pump polarization of the nonlinear refractive index in CS2 and its dilute solutions using a femtosecond time division interferometer. The temporal profiles of n(2 parallel to)(t) and n(2 perpendicular to)(t) were decomposed into the electronic, fast- and slow-decay nuclear contributions based on the response time. The magnitudes, signs and time constants of these three contributions of n(2 parallel to)(t) and n(2 perpendicular to)(t) were also evaluated with high accuracy. Moreover, the n(2 parallel to)(t) and n(2 perpendicular to)(t) measurements in the dilute CS2 solutions showed that the ratio between the fast-decay contributions of time responses of n(2 parallel to)(t) and n(2 perpendicular to)(t) was the same value as that between the slow-decay contributions. This result is explained using a cluster model.
  • Fujiwara, T., Kamoshida, T., Morita, R. and Yamashita, M. : "Temporally-Separated Ultrafast-Emission Dynamics of Neutral and Cationic Molecules in Guanine and its Derivatives Aqueous Solutions", J. Photochem. Photobiol. B : Biol, 41 : 114-121 (1997)*
    1997年 [査読無し][通常論文]
  • T Saito, Y Yamaoka, Y Kimura, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 35 9A 4649 - 4653 1996年09月 [査読無し][通常論文]
     
    For the crystal and solution of 1-(3-thienyl)-3-(4-chlorophenyl)propene-1-one (TCPP), which is transparent over the whole visible region, the nonresonant third-order nonlinear dynamics is investigated by time-resolved degenerate four-wave mixing spectroscopy. The temporal nonlinear behaviors of both crystal and solution exhibit the instantaneous responses during 80 fs excitation at around 625 nm. The third-order nonlinear susceptibilities are determined to be \chi(bbbb)((3))\ = 7.1 x 10(-13) esu for crystal and \chi(llll)((3)TC)\ = 7.1 x 10(-14) esu at 1 mol/l for solution. This suggests that the TCPP crystal has a large value of chi((3))/alpha tau = 2.4 x 10(3) esu . cm . s(-1) under the assumption of the nonlinear response time tau = 30 fs (absorption coefficient alpha = 0.01 cm(-1)), which is a parameter important for ultrafast optical control materials. The obtained \chi(bbbb)((3))\ value satisfies an already known relationship between the second- and third-order susceptibilities.
  • 山下幹雄, 曽根宏靖, 森田隆二
    応用物理学関係連合講演会講演予稿集 35 9B L1194 - L1197 1996年09月 [査読無し][通常論文]
     
    An approach for generation of an ultrabroad-band optical pulse (similar to 550 THz width) is proposed, which is based on mutual induced phase modulation of three synchronized femtosecond pulses in a short fiber. These pulses having equidistant carrier frequencies and constant carrier-phase differences are obtained from the fundamental (omega(01)), the second-harmonic (2 omega(01)) and the second-harmonic-pulse pumped parametric (3 omega(01)/2) waves, These are generated under the phase-matched, frequency-conserved and gain-maximized conditions by one common femtosecond pulse. Computer analysis shows that chirp of the composite wave at the tiber output can be compensated for by a spatial phase modulator and a 1.76-cycle pulse is generated.
  • T Itoh, R Morita, M Yamashita
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 35 9A L1107 - L1110 1996年09月 [査読有り][通常論文]
     
    Temporal spectral dynamics of nonlinear propagation of similar to 80 femtosecond optical pulses is investigated experimentally and analytically for the first time for two single-mode glass fibers of GeO2-doped fused silica and Er:GeO2-doped fused silica. Comparison between experimental and analytical results enables us to determine the nonlinear refractive indices and their response times to be 2.4 x 10(-13) esu and 1.8 fs, respectively: for the former fiber and 4.0 x 10(-13) esu and 2.1 fs, respectively, for the latter fiber. This suggests that these fibers are more efficient for compression of extremely short pulses than the conventional fused-silica fiber.
  • Y. Yamaoka, T. Saito, Y. Sato, R. Morita and M. Yamashita : "Dynamics of third-order nonlinearity of nonresonant organic solutions by femtosecond pump-probe spectroscopy", Nonlinear Optics, 15(1-4) : 61-64(1996)*
    1996年 [査読無し][通常論文]
  • T. Itoh, R. Morita and M. Yamashita : "Extremely fast-response, highly nonlinear doped-silica single-mode fibers", Jpn. J. Appl. Phys., 35(9A) : L1107-L1110 (1996)*
    1996年 [査読無し][通常論文]
  • Yoshihisa Yamaoka, Takeshi Saito, Yasuhiro Sato, Ryuji Morita, Mikio Yamashita
    Molecular Crystals and Liquid Crystals Science and Technology Section B: Nonlinear Optics 15 1-4 61 - 64 1996年01月01日 [査読無し][通常論文]
     
    We measured a response of the third-order susceptibility X(3) (t) of an organic material 4-(N, N-diethylamino)-β-nitrostyrene / N, N-dimethyl-formamide solution in the non-absorption region by use of femtosecond time-resolved degenerate four-wave mixing spectroscopy. The results indicate the response of X(3) (t) consists of two molecular components with time constants of 150 - 180 fs and several ps, as well as an electronic component. Moreover, we measured a clean negative response of n2⊥ for CS2 using a femtosecond interferometer.
  • R MORITA, M YAMASHITA
    OPTICS LETTERS 19 18 1459 - 1461 1994年09月 [査読有り][通常論文]
     
    We investigate the effect of delayed nonlinear response time on pulse compression, using an organic crystal-cored fiber in the normal dispersion region. With up to third-order phase compensation, a 100-W, 100-fs hyperbolic-secant pulse is compressed to similar to 10 fs with a delayed nonlinear response time as well as without it. It is shown that third-order phase adjustment can compensate for the phase asymmetry in the frequency domain that is induced by the effect of the delayed nonlinear response.
  • R MORITA, M YAMASHITA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 32 7A L905 - L907 1993年07月 [査読有り][通常論文]
     
    A simple semitheoretical relation between ultrafast nonlinear susceptibilities chi(2) and chi(3) due to the electronic polarization in the nonresonant region for noncentrosymmetric materials is derived. This result well explains experimental data.
  • 森田隆二, 山下幹雄
    応用物理学関係連合講演会講演予稿集 32 7 L905 - L907 1993年 [査読有り][通常論文]
     
    A simple semitheoretical relation between ultrafast nonlinear susceptibilities χ (2) and χ (3) due to the electronic polarization in the nonresonant region for noncentrosymmetric materials is derived. This result well explains experimental data. © 1993 The Japan Society of Applied Physics.
  • T. Kondo, N. Hashizume, K. Tsuda, R. Morita, N. Ogasawara, S. Umegaki, R. Ito
    International Journal of Nonlinear Optical Physics 1 2 367 - 392 1992年 [査読有り][通常論文]
  • T KONDO, N HASHIZUME, S MIYOSHI, R MORITA, N OGASAWARA, S UMEGAKI, R ITO
    NONLINEAR OPTICAL PROPERTIES OF ORGANIC MATERIALS III 1337 53 - 59 1990年 [査読有り][通常論文]
  • Takashi Kondo, Ryuji Morita, Nagaatsu Ogasawara, Shinsuke Umegaki, Ryoichi Ito
    Japanese Journal of Applied Physics 28 9 R 1622 - 1628 1989年09月01日 [査読有り][通常論文]
     
    A nonlinear optical organic material, (-)2-(α-methylbenzylamino)-5-nitropyridine (MBANP), has been comprehensively investigated with the objective of application to frequency doubling of laser diodes. Its molecular hyperpolarizability is as large as that of p-nitroaniline. MBANP crystallizes with a highly asymmetric molecular arrangement. The largest nonlinear optical coefficient, d22, is measured to be 60 pm/V. The corresponding figure of merit for frequency doubling at 1.064 µm is 3.5 times larger than that for d33of LiNbO3. Čerenkov-radiation-type, phase-matched second-harmonic generation has been demonstrated utilizing the d22coefficient by making use of an appropriate waveguiding structure. © 1989 The Japan Society of Applied Physics.
  • Ryuji Morita, Nagaatsu Ogasawara, Ryoichi Ito, Shinsuke Umegaki
    Proceedings of SPIE - The International Society for Optical Engineering 971 260 - 267 1988年12月21日 [査読有り][通常論文]
     
    Results of measurement of the dispersion of the second-order optical nonlinear coefficient d11 of 2-methyl-4-nitroaniline (MNA) using laser diodes as light sources are presented over a wavelength range of 1.20 to 1.54 μm. The nonlinear optical coefficient strongly depends on wavelength, exhibiting a resonance enhancement. We also report the first observation of multiple-reflection effects in optical second-harmonic generation. The observation has been made possible by the use of a single-mode laser diode as a light source. The experimental results are in excellent agreement with a theoretical analysis which takes account of the multiple reflections of both the fundamental and second-harmonic waves. © 1988 SPIE.

書籍

  • トポロジカルオプティクス
    森田 隆二, 尾松 孝茂, 戸田 泰則 (担当:分担執筆)
    朝倉書店 2016年
  • Over 1-mJ intense ultrashort optical-vortex pulse generation with programmable topological-charge control by chirped-pulse amplification
    K. Yamane, A. Honda, Y. Toda, R. Morita (担当:分担執筆範囲:809-812)
    Springer 2015年
  • Laser Spectroscopy Using Topological Light Beams
    Y. Toda, R. Morita (担当:分担執筆範囲:83-117)
    Springer 2015年
  • Chiral Nanostructures Fabricated by Twisted Light with Spin
    T. Omatsu, R. Morita (担当:分担執筆範囲:311-334)
    Pan Stanford Publishing 2014年
  • トポロジーデザイニング~新しい幾何学からはじめる物質・材料設計~
    エヌ・ティー・エス 2009年
  • Mono-cycle photonics and optical scanning tunneling microscopy---route to femtosecond-angstrom technology---
    Springer Verlag 2005年

講演・口頭発表等

  • Direct print of well-aligned close-packed gold microdots with optical vortex irradiation  [通常講演]
    Kanta Takahashi, Haruki Kawaguchi, Rong Wei, Keisaku Yamane, Ken-ichi Yuyama, Satoyuki Kawano, Ryuji Morita, Nobuyuki Aoki, Katsuhiko Miyamoto, Takashige Omatsu
    CLEO Pacific-Rim 2022 2022年08月 口頭発表(一般)
  • Direct Optical Vortex Laser Printing of a Microdot with Close-Packed and Sintered Gold Nanoparticles  [通常講演]
    Haruki Kawaguchi, Rong Wei, Keisaku Yamane, Ken-ichi Yuyama, Satoyuki Kawano, Ryuji Morita, Kohei Toyoda, Katsuhiko Miyamoto, Takashige Omatsu
    CLEO 2022 2022年05月 口頭発表(一般)
  • Development of sub-Gfps ultrafast snapshot imaging system based on recirculation filtering of ultrashort optical pulses  [通常講演]
    Asami Honda, Keisaku Yamane, Masato Suzuki, Jin Kawaguchi, Yasunori Toda, Takashige Omatsu, Ryuji Morita
    CLEO 2022 2022年05月 口頭発表(一般)
  • Direct print of close-packed gold nanoparticle microdots with optical vortex illumination  [通常講演]
    H. Kawaguchi, K. Takahashi, R. Wei, K. Yamane, K.-i. Yuyama, S. Kawano, R. Morita, N. Aoki, K. Miyamoto, T. Omatsu
    8th Optical Manipulation and Structured Materials Conference (OMC2022) 2022年04月 口頭発表(一般)
  • 再循環光学フィルタリングを用いた sub-Gfps イメージング装置の開発  [通常講演]
    爲本龍太, 本田亜沙美, 山根啓作, 鈴木 雅人, 戸田泰則, 尾松孝茂, 森田隆二
    第69回応用物理学会春季学術講演会 2022年03月 口頭発表(一般)
  • 光渦レーザー誘起前方転写法による金ナノインクプリンティング  [通常講演]
    魏 榕, 川口晴生, 山根啓作, 柚山健一, 川野聡恭, 森田隆二, 青木伸之, 宮本克彦, 尾松孝茂
    第69回応用物理学会春季学術講演会 2022年03月 口頭発表(一般)
  • 時間-周波数マッピングに基づく新規高速スナップショット計測システムの開発  [通常講演]
    本田亜沙美, 山根啓作, 鈴木雅人, 川口秦, 戸田泰則, 尾松孝茂, 森田隆二
    レーザー学会学術講演会 第42回年次大会 2022年01月 口頭発表(一般)
  • Vortex Airy beam realized by superposition of two Airy beams  [通常講演]
    Masato Suzuki, Keisaku Yamane, Takashige Omatsu, Ryuji Morita
    Frontiers in Optics 2021 2021年11月 口頭発表(一般)
  • Haruki Kawaguchi,Kei Umesato,Kanta Takahashi,Keisaku Yamane,Ken-ichi Yuyama,Satoyuki Kawano,Ryuji Morita,Katsuhiko Miyamoto,Takashige Omatsu  [通常講演]
    Optical vortex, induced gold nanoparticles forward transfer
    Joint Symposia on Optics Program, Optics and Photonics Japan 2021 2021年10月 口頭発表(一般)
  • エアリービームの重ね合わせによる光渦エアリービームの生成の検討  [通常講演]
    鈴木雅人, 山根啓作, 尾松孝茂, 森田隆二
    Optics and Photonics Japan 2021 2021年10月 口頭発表(一般)
  • Spectroscopic polarization measurement and control using channeled spectrum  [通常講演]
    Kazuhiko Oka, Keisaku Yamane, Moritsugu Sakamoto, Ryuji Morita
    Optical Technology and Measurement for Industrial Applications Conference 2021 2021年10月 口頭発表(一般)
  • Proposal of new-type vortex Airy beam with improved propagation characteristics  [通常講演]
    Masato Suzuki, Keisaku Yamane, Takashige Omatsu, Ryuji Morita
    JSAP-OSA Joint Symposia 2021 2021年09月 口頭発表(一般)
  • Optical vortex induced hexagonal close-packed photonic-microring  [通常講演]
    K. Takahashi, H. Kawaguchi, K. Umesato, Y. Arita, K. Yamane, R. Morita, K.-i. Yuyama, S. Kawano, K. Miyamoto, T. Omatsu
    JSAP-OSA Joint Symposia 2021 2021年09月 口頭発表(一般)
  • Creation of hexagonal close-packed photonic-ring with optical vortex  [通常講演]
    K. Takahashi, H. Kawaguchi, K. Umesato, Y. Arita, K. Yamane, R. Morita, K.-i. Yuyama, S. Kawano, K. Miyamoto, T. Omatsu
    The 40th JSST Annual International Conference on Simulation Technology 2021年09月 口頭発表(一般)
  • Improvement in orbital angular momentum mode sorting of optical vortices  [通常講演]
    K. Yamane, K. Iitsuka, M. Sakamoto, H. Ono, K. Oka, Y. Toda, R. Morita
    CLEO Europe/Europe-EQEC 2021年06月 口頭発表(一般)

その他活動・業績

特許

  • 特許5164151:軸対称偏光レーザー発振装置及び軸対称偏光レーザー発振方法    2012年12月28日
    尾松孝茂, 森田 隆二
  • 軸対称偏光レーザー発振装置および軸対称偏光レーザー発振方法
    特開2009-188361
  • 光渦発生装置、微小物体操作装置、天体探査装置および偏光渦変換素子
    WO 2007/013648
  • Delay time modulation femtosecond time-resolved scanning probe microscope apparatus
    7002149
  • Ultra-broadband, variable and multiple wavelength, pulse waveform shaping apparatus
    1241513
  • Ultra-broadband, variable and multiple wavelength, pulse waveform shaping apparatus
    6,826,209
  • Ultra-broadband, variable and multiple wavelength, pulse waveform shaping apparatus: Morita, R., Yamashita, M., Suguro, A., Morokawa, S. (2002)
    6,826,209

受賞

  • 2017年04月 応用物理学会 2016年度(第15回) APEX/JJAP編集貢献賞受賞
     
    受賞者: 森田 隆二
  • 2016年09月 日本学術振興会 科学研究費助成事業 審査員表彰
     
    受賞者: 森田 隆二
  • 2016年09月 応用物理学会 第10回(2016年度) フェロー表彰
     「超短光パルスにおけるトポロジーの制御と精密計測」 
    受賞者: 森田 隆二
  • 2015年09月 応用物理学会 第37回(2015年)応用物理学会優秀論文賞
     
    受賞者: 森田 隆二
  • 2012年05月 アメリカ光学会 シニアメンバーに選任・表彰
     
    受賞者: 森田 隆二
  • 2010年10月 日本学術振興会 科学研究費助成事業 審査員表彰
  • 1990年08月 フランス政府 給費留学研究員
     
    受賞者: 森田 隆二

共同研究・競争的資金等の研究課題

  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2023年04月 -2026年03月 
    代表者 : 森田 隆二
  • チャープした超短光渦パルスの重ね合わせによる超高速ビームパターン変調とその応用
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 森田 隆二
  • 光圧を極める:分子操作の極限化と光制御によるマクロ化
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2016年06月 -2021年03月 
    代表者 : 笹木 敬司, 村越 敬, 森田 隆二, 深港 豪, 山根 啓作
     
    本研究では、分子・分子集合体に作用する光圧をナノ空間で自在にデザインし、室温・媒質中においてナノ物質を個別選択的に捕捉・操作し、配置・配向・配列を制御する技術を世界に先駆けて開発するとともに、多様な光圧制御技術により光物質操作のマクロ化を実現する事を目的としている。 今年度は、昨年度に引き続き、高精度の金ナノ構造の作製および光圧を発生させるためのナノ局在場のデザインを行うため、開発した数値解析手法を用いて金ナノトライマー構造の局在場の解析を進めた。この知見と昨年度の技術的なノウハウを基に、実際に電子線描画装置を用いて水中で波長1064nmに共鳴を持つ金ナノボウタイ構造を作製した。10nm程度のサイズのナノギャップ部への選択的な発光体の導入を試みるため、この試作構造に水中で波長1064nmの直線偏光レーザーを照射し、ナノ粒子の捕捉を試みた。実験では、直径40nmの色素分子凝集体を用いて光捕捉を行った結果、ナノ粒子が数μmの距離から急激にギャップ部に引き寄せられ、捕捉される様子を確認した。照射レーザーを切った後もギャップ部においてナノ粒子からの蛍光が確認され、乾燥した試料のSEM像からもギャップ部に選択的にナノ粒子が堆積している様子が確認できた。また、昨年度構築したテーパーファイバーを用いたナノ粒子捕捉・輸送システムを用い、異なる波長の対向ビームの入射による捕捉粒子(NVセンター含有・非含有ナノダイヤモンド)の吸収特性を利用したナノ粒子操作・選別を試みた。粒子に作用する散乱力は、対向ビームによりキャンセルされ、吸収量の違いによる吸収力の差の分だけ、NVセンター含有・非含有粒子間の運動に差が生じる。入射レーザー光強度の最適化を行なった結果、NVセンターの有無により輸送される方向が反転し、NVセンター含有・非含有ダイヤモンドナノ粒子の選別が可能となることを示した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 森田 隆二, 戸田 泰則
     
    モノサイクル域で軌道角運動量可変な高強度超短光渦パルス(パルスエネルギー 1 mJ超,パルス幅 27fs)の発生に成功し,また, 2つの直交偏光光渦パルスをコヒーレントビーム結合させることにより,超広帯域偏光渦パルス(波長帯域750-880 nm)の生成に成功した。さらに,超広帯域偏光渦パルスの偏光対称性,空間的偏光純度に関する精密測定法の開発を行い,その有効性を実証した。また,径偏光超短パルスによる半導体のスナップショット偏光分光実験を行い,この手法の高精度・高感度特性を実証した。
  • トポロジカル光波の全角運動量を利用した新規物性制御
    科学技術振興機構:戦略的創造研究推進事業CREST(受託研究)
    研究期間 : 2010年10月 -2016年03月 
    代表者 : 森田 隆二
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2011年04月 -2014年03月 
    代表者 : 森田 隆二, 戸田 泰則
     
    サイクル域の光渦パルスの発生,ならびに軌道角運動量可変な超mJ高強度・27 fs超短光渦パルス発生に初めて成功し,また超広帯域光渦パルスの高精度軌道角運動量スペクトル準実時間測定を実証した。さらに,光渦を用いたポンプ・プローブ閉ループ時間分解非線型励起分光法を開発し,GaN励起子の軌道角運動量の緩和時間を評価した。その他,スピン角運動量および軌道角運動量を制御した光渦パルスを用いて,ナノサイズの金属螺旋ニードル構造を作製することにも初めて成功した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2010年04月 -2013年03月 
    代表者 : 目良 裕, 森田 隆二, 近藤 高志
     
    物質表面のエネルギー構造の時間分解ダイナミクスを、ナノスケールの空間分解能で測定可能なシステムを試作する目的で、超短パルスレーザーから作るスーパーコンティニュアム広帯域光源とフーリエ変換干渉計を走査トンネル顕微鏡(STM)と組み合わせた新しい電場変調測定手法を提案し、実現した。この測定法を用いることで、半導体のエネルギー構造が測定できることを示した。 また短パルスレーザーとSTMを組み合わせて半導体表面における電子や空孔のダイナミクスを測定する際の基礎となる物理過程をモデル化し、数値計算でシミュレーションした結果を実験結果と比較することで、物理量を正しく評価するための条件を明らかにした。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2011年 -2012年 
    代表者 : 森田 隆二
     
    光渦パルスをシード光とし,縮退光パラメトリック増幅およびチャープ補償を行うことにより,サイクル域の光渦パルスの発生に初めて成功した。また,軌道角運動量可変な超短光渦パルス発生ならび高精度軌道角運動量スペクトル測定法の開発も行った。さらに,光渦を用いたポンプ・プローブ閉ループ時間分解非線型励起分光法および高精度軌道角運動量変換法を開発し,物質との相互作用としては,スピン角運動量および軌道角運動量を制御した光渦パルスを用いて,ナノサイズの金属螺旋ニードル構造を作製することに初めて成功した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2008年 -2010年 
    代表者 : 森田 隆二, 戸田 泰則
     
    表面相互作用の異なる金属基板上での光異性化前後アゾベンゼン単分子について,走査トンネル顕微鏡による観測を行い,表面相互作用の強い基板上では平面構造のトランス体が存在し,この場合,異性化過程において反転機構が支配的であることを見出した。また,光異性化,分子コンフォメーション変化を促す新たな光源として,時間・周波数領域極限位相・振幅制御だけでなく,ビーム内空間位相・偏光の制御を行った光波の高効率発生に成功,それを用いたリング状非線型分光法を確立し,さらには金属との相互作用実験により,光の全角運動量の効果を初めて明らかにした。
  • 日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2007年 -2008年 
    代表者 : 森田 隆二
     
    本研究は、申請者らが現在までに独自に開発したモノサイクル域光パルス(光の振動周期とパルス幅が同程度の光パルス)発生・制御技術を「巨大加速度を発生させる手法」としてとらえること、ならびにスピン角運動量(偏光に対応)だけではなく新たなパラメータである軌道角運動量(光の位相がビーム断面内方位角に依存することに対応)を制御した光である「光渦(optical vortex)」および偏光分布が空間依存する典型的な光である「偏光渦(polarization vortex)」という概念と結合させることを目的としている。 本年度は、モノサイクル域光渦パルスの発生を目指して、以下の無分散光渦パルスの発生実験、高出力軸対称偏光レーザーの開発を行った。 1.従来の超広帯域光渦パルス発生法では、空間分散が生じる、すべての周波数帯域においてトポロジカルチャージがそろわない、といった問題が生じる。これら問題を克服する手法として、軸対称偏光板を用い、空間的に偏光特異性をもつビームを発生させることによる、独自の無分散光渦パルス発生法を考案、また、本手法による超広帯域光渦パルス発生実験を行うことにより、その有効性を実証した。さらには、この手法のJonesベクトルによる解析も行った。 高出力光渦パルスの発生を目指し、半導体レーザー横方向励起バウンス型Nd : GdVO_4の作製を行った。本方法は、励起の手法を制御することにより、高次モードであるLaguerre-Gaussモード発振をさせて、55Wの励起光に対して17.8Wの高出力を得ている。このような高次モード発振に関してモード整合効率の解析も行っている。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2004年 -2007年 
    代表者 : 山下 幹雄, 森田 隆二, 勝呂 彰
     
    10^<-15>秒域の光電場波束の発生・計測・制御を中心に研究を行った。その結果、自己位相変調(SPM)法により、可視域で世界最短のフーリエ変換限界単一パルス2.8fs・1.5サイクル光の発生に成功した。さらに、独自な誘起位相変調 (IPM) 法により、2.6 fs・1.3サイクル・1.4 GW光の発生に成功した。また、搬送波・包絡波位相 (CEP) を安定化したl kHz繰り返しの、3.3 fs・1.7サイクル光電場波束発生に成功した。加えて、フォトニッククリスタルファイバー (PCF) 法を用いた光パルス圧縮法としては、最短のサブ5 fsの光パルス発生が可能であることを実証した。これらは、一オクターブを越える帯域を有しかつ準実時間動作する、独自な自律型フィードバックチャープ補償システム(スペクトル位相を操作する空間位相変調器(SLM)+4f光学配置、スペクトル位相信号を高感度測定をするM-SPIDER、作成したプログラムによるスペクトル位相解析とSLM駆動のための計算機から成っている)の構築により可能となった。また、スペクトル位相解析にウェーブレット変換法を用いることにより、フィードバック補償の自動化と高精度スペクトル位相解析が可能であることを示した。さらにこのシステムの帯域を、紫外にまで拡げるため、新しい液晶を用いた空間光変調(SLM)素子を試作し、その位相変調特性の詳細な解明と有用性を確認した。 一方、10^<-15>秒光電場波束の石英ファイバー非線形伝播について包絡波近似などのない厳密な非線形波動方程式を数値解析した。その結果、入射光CEPに著しく依存する第3高調波発生が見いだされた。これは、簡便なCEP計測法として利用できる現象である。
  • 極限時間域トポロジカル光波の発生と非線形光学
    研究期間 : 2007年
  • 日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2005年 -2006年 
    代表者 : 森田 隆二
     
    本年度は、光渦発生ならびにサイクル域光パルスに関する以下の成果を得た。 1.チタニウムナファイアレーザー発振器からの〜50fsの光パルスを、2次元空間位相変調器により作製したホログラムに入射、回折させることにより、〜50fsの光渦パルスを発生させた。この発生した光渦パルスの空間分解スペクトルを測定し、空間チャープを評価した。その結果、〜50fs程度の光パルスでは、空間チャープが無視できるほど小さいことを明らかにした。 2.〜50fsのエルミートガウシアンビームパルスを参照光とし、これを被測定対象である〜50 fs光渦(ラゲールガウシアン)ビーム内で集光・走査することにより、空間分解された相互相関周波数分解ゲート信号を測定し、光渦パルスの時空間特性を定量的に評価した。この結果は光渦パルスを用いた分光測定などの応用の際、重要となる。 3.光渦に非対称欠陥を導入することにより、トポロジカル位相の一種であるグイ位相の、集光にともなうシフトを直接観測する手法を開発した。この手法は、従来の干渉による手法とは異なり、簡便に光渦の本質的物理量であるグイ位相を求めることができる。 4.断面内に、2つの光渦が存在するようなビームを発生させ、その空間発展を観測した。ビーム焦点付近で通常の渦運動と異なる新たな振る舞いを発見した。現在、そのメカニズムの解明を進めている。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2004年 -2006年 
    代表者 : 森田 隆二, 郷原 一寿, 戸田 泰則
     
    1.自己位相変調効果を用いて、1オクターブを超える超広帯域スペクトル(460-1060nm)を有する光パルスを発生し、独自に作製した、変形スペクトル干渉位相電場再生システムおよびフィードバック位相補償システムによるフィードバック位相補償を行うことにより、2.8fs,1.5サイクルのフーリエ変換限界光パルスの発生に成功した。これは、スペクトル位相が決定された可視・赤外領域における世界最短パルスである。 2.生体物質の3次元空間分解観測に適用可能な光第2高調波レーザー顕微鏡を開発し、ラット胎児大脳皮質由来の神経細胞の観察を行った。細胞体の空間反転対称性の破れを反映した信号を観測することにより、核、軸索からの強い信号の観測に成功している。現在、空間分解能は、1.5μm程度である。 3.フェムト秒光パルスレーザー増幅器を光源としたコヒーレント反ストークスラマン散乱レーザー顕微鏡の開発を行った。波長800nmと1040nmの光を用いて、650nmのCARS信号光を検出することにより、タマネギ表皮細胞の2900cm^<-1>のC-H伸縮振動、波長800nmと1100nmの光を用いて、630nmのCARS信号光を検出することにより3400cm^<-1>のN-H伸縮振動を空間分解観測した。その結果を比較することにより、C-Hリッチ、N-Hリッチな領域のマッピングを行った。 4.メチルレッドをインターカレートしたDNAの二重鎖の結合、解離を光第2高調波顕微鏡のようなマクロな測定により観測することを試みた。そのメカニズムは、結合している場合二重鎖は反転対称性を持ち、解離している場合反転対称性が破れ、光第2高調波活性になることによる。現在、信号レベルと雑音レベルが同程度で有意な結果が得られていないが、非線形性の大きなアゾ色素を用いることにより、信号強度の向上を図っている段階である。
  • 日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2003年 -2004年 
    代表者 : 森田 隆二
     
    本年度は、サイクル域光パルスに関する以下の成果を得た。 1)自己位相変調効果を用いて、1オクターブを超える超広帯域スペクトル(460-1060nm)を有する光パルスを発生し、研究者らが独自に作製した、変形スペクトル干渉位相電場再生システムおよびフィードバック位相補償システムによるフィードバック位相補償を行うことにより、2.8fs,1.5サイクルのフーリエ変換限界光パルスの発生に成功した。これは、スペクトル位相が決定された可視・赤外領域における世界最短パルスである。 2)サイクル域の光パルスと物質の相互作用を考える場合、搬送波・包絡波位相の制御が重要となる。基本波・第2高調波自己位相参照干渉スペクトル測定装置、位相ロックループを用いて搬送波・包絡波位相を安定化した超オクターブ帯域3.3fs,1,7サイクル光パルスの発生に成功した。これは、搬送波・包絡波位相が安定化された世界最短パルスである。 3)微細構造ファイバーであるフォトニック結晶ファイバー中にフェムト秒光パルスを伝播させることにより、620-945nm超広帯域スペクトルを発生させ、変形スペクトル干渉位相電場再生システム、フィードバック位相補償システムを組み合わせたフィードバック位相補償を行い、フォトニック結晶ファイバーからでは世界最短の5.8fs(2.3サイクル)の高繰り返し光パルスの発生に成功した。 4)フェムト秒レーザーと走査トンネル顕微鏡を結合させ、フェムト秒時間分解トンネル電流の測定に成功した。この測定には、時間遅延を変調したフェムト秒パルス対を用い、試料としては低温成長GaNAsを用いた。試料は、653fsと55.1psの2つの高速緩和過程を示し、これらの結果は、従来のポンプ・プローブ法による光学測定の結果と一致し、本測定法の妥当性を示している。
  • 位相・偏光特異点を有する光の時空間特性
    研究期間 : 2004年
  • 日本学術振興会:科学研究費助成事業 萌芽的研究
    研究期間 : 2000年 -2001年 
    代表者 : 森田 隆二
     
    本年度は、サイクル域光パルスに関する以下の成果を得た。 1.石英ファイバー中の12fs(4.5サイクル)光パルスの非線形伝播に関して、すべての次数の分散、遅延ラマン応答を含む非線形応答を取り込んだ時間領域有限差分(FDTD)法による計算を行い、別に行った実験結果をよく再現する結果を得た。この結果から、12fsのような時間領域では、石英ファイバーの遅延応答ラマン効果を考慮することが重要であることを見いだした。 2.アルゴンガス充填ファイバー中に、チタニウムサファイアレーザー増幅器からのフェムト秒光パルス(基本波,中心波長780nm)を伝播させ、自己位相変調効果を効率的に生じさせることにより超広帯域コヒーレント光波発生を発生する。この光波を、回折格子、凹面鏡、空間位相変調器によって構成される4f-非線形チャープ補償光学系により位相補償した。この空間位相変調器のみによる位相補償により、従来用いられてきたフリンジ分解自己相関法より正確な周波数分解光ゲート装置を用いた測定では世界最短パルス幅5.0fs、サイクル数2.2サイクルの極短光パルスの発生に成功した。 3.上記周波数分解光ゲート装置よりもより広帯域光パルスを測定可能な電場再構築スペクトル干渉装置を作製し、世界最短パルス幅5.0fs、サイクル数2.2サイクルの極短光パルスの発生に成功した。また、この方法により、1オクターブを超える超広帯域パルスの電場振幅・位相の測定にも成功している。 4.高エネルギー領域の振動状態を効率よくコヒーレントに選択励起する手法として、その振動状態周波数とパルス列繰り返し周波数、ならびに光周波数差とを同時に一致させた2色フェムト秒パルス列励起法の提案を行い、この手法に我々が行っている波長多重波形整形技術が有用であることを示した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 1999年 -2000年 
    代表者 : 山下 幹雄, 大谷 守正, 森田 隆二
     
    包絡波近似(SVEA)を越えた非線形光学現象の研究として、1.数100THz以上の超広帯域コヒーレント光波の発生、 2.光パルスのモノサイクル化、3.極限時間域の光波計測の研究を行い、以下のような成果を得た。 1.超広帯域コヒーレント光波の発生 (1)独自なシングルモード(SM)キャピラリーファイバー誘起位相変調(IPM)による300〜1000nm(Δν=700THz)の光波発生に成功→0.9サイクル・1.5fsTLパルスに対応→位相が確定した最広帯域コヒーレント光波 (2)独自なSM石英ファイバーIPMによる490〜900nm(Δν=290THz)および670〜1250nm(Δν=290THz)の光波発生に成功→1.9サイクル・4.0fsおよび1.5サイクル・4.2fsTLパルスに対応→SM石英ファイバーでは最広帯域コヒーレント光波 (3)IPM特有のスペクトル振動構造の初の観測とその起因の理論的解明 (4)IPM超広帯域光波の基本位相特性の解明 (5)SMファイバー中のSVEAフリー非線形光波伝搬の理論・実験両面からの解明 2.光パルスのモノサイクル化 (1)独自な空間位相変調法(SLM)による4.1fs・1.78モノサイクル台光パルス発生に成功→世界最短(4.0fs)レベル達成 (2)独自なプリズム対+プリズム分散SLMによる4.9fs・2.06サイクル光パルス発生に成功 (3)独自なプリズム対+回折格子分散SLMによる6.0fs・2.4サイクル光パルス発生に成功 (4)同様な手法による75MHz高繰り返し、7.1fs・2.7サイクルTL光パルス発生に成功 (5)7fs台光パルスの3次位相分散特性の実験的解明 (6〉IPM超広帯域光波のSLMによるチャープ補償基礎実験に成功 (7)現実的なSVEAフリー非線形光波伝搬解析による510asアト秒光パルス発生の定量提案 3.極限時間域の光波計測 (1)試作SH・FROG装置および試作SPIDER装置により、5.0fs光パルス波形I(t)・位相変化ψ(t)測定に成功→後者についてはこれまでの最短パルス測定であり、オクターブを越えたスペクトルパルスのI(t)・ψ(t)測定が可能 (2)高感度変形SPIDER法の提案と基礎実験実証に成功
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1997年 -1998年 
    代表者 : 森田 隆二
     
    本研究の目的は、系の励起状態量子波束を自由に制御できるようなフェムト秒光パルス(tailored femtosecond optical pulse)の発生法を開発すること、ならびに、得られたtailored femtosecond optical pulseを用いて、現在までに行ってきたポンプ・プローブ測定技術を発展させた、系の励起状態量子波束の制御を行うことである。本年度は、1.2次元空間位相変調器を用いたフェムト秒光パルスの同時異波形整形実験、2.整形フェムト秒光パルスによる励起状態量子波束運動制御、特にコヒーレント・フォノン選択励起の計算機実験を行った。・1. まず、2次元空間位相変調器を用いたフェムト秒光パルスの同時異波形整形実験を行った。円筒レンズ対により一方向(x方向とする)に伸びた形でコリメートしたフェムト秒レーザーパルスを、回折格子、円筒レンズからなるフーリエ光学系を用いて、x方向と直交するy方向に周波数分解することにより、x方向には空間的に、y方向には周波数分解された2次元的ビームができる。この2次元的ビームの各点において、2次元空間位相変調器を用いて、異なる位相変調を加えることにより、フェムト秒光パルスを同時に、複数の異波形に整形することに成功した。これは、広帯域フェムト秒光パルスを切り出した後、2次元波形整形する、多波長同時波形整形の基礎となる実験結果...
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1997年 -1997年 
    代表者 : 森田 隆二, 水野 誠司
     
    本研究は、大きな非線形性を持つ有機材料の利点を生かしつつ、機械的なもろさを克服することのできる可能性のある有機・無機ゾル・ゲル薄膜を用いて非線形光学効果を利用した光変調デバイスを開発することである。 そこで、本年度は、有機材料としてシアニン色素S120のLB膜に注目し、1.シアニン色素(S120)LB膜の電場変調吸収測定、2.シアニン色素(S120)LB膜の3次非線形感受率χ^<(3)>の波長分散の決定を行った。また、CS_2の負の時間応答非線形屈折率効果に着目し、3.CS_2液体ファイバーを用いた新規フェムト秒パルス圧縮法の提案を行った。 ・1.シアニン色素S120のLB膜を作製し、これらの電場変調吸収測定を行った。測定された電場変調スペクトルは、J会合することによる線形吸収ピーク(J-バンド)に対応した鋭い形状を有すること、また、形状が線形吸収スペクトルのエネルギー2階微分係数とほぼ相似であり、非線形性発現メカニズムは、Frenkel型excitonが寄与する1次のシュタルク効果(基底状態と励起状態の永久双極子モーメントの差で表される)により説明されることを明らかにした。 ・2.測定された電場変調吸収スペクトルとクラマ-ス・クロニヒ変換を用いた技法により、シアニン色素LB膜ののχ^<(3)>の波長分散を450-700nmにおいて決定した。この結果、シアニン色素LB膜は、共鳴域では|χ^<(3)>|=2.8×10^<-10>esu,非共鳴域においては|χ^<(3)>|=2.4×10^<-12>esuと大きな値を持つことが明らかとなり、高効率光変調デバイスへの応用が期待される。 ・3.正常分散域において負の時間応答非線形屈折率効果を用いたCS_2液体ファイバーによる新規フェムト秒光パルス圧縮法を提案し、その有用性を計算機実験により明らかにした。この方法は、従来の石英ファイバーを用いた圧縮法と同程度の圧縮効率を有し、かつ、外部位相補償を必要としないという利点を持つ。
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1996年 -1996年 
    代表者 : 森田 隆二, 水野 誠司
     
    本研究は、大きな非線形性を持つ有機材料の利点を生かしつつ、機械的なもろさを克服することのできる可能性のある有機ゾル・ゲル薄膜を用いて非線形光学効果を利用した光変調デバイスを開発することである。 そこで、本年度は、有機材料としてカロテノイド、アゾベンゼンに注目し、1.カロテノイドを用いた有機・無機ゾル・ゲルの作製、ならびにその非線形光学特性の時間分解測定、2.アゾベンゼン2分子膜の電場変調吸収測定、3.アゾベンゼン2分子膜の3次非線形感受率_χ^<(3)>の波長分散測定を行った。 ・1.テトラエトキシシラン、エタノールを用いて有機材料β,β-カロテンをドープした有機・無機ゾル・ゲルを作製し、光ヘテロダイン検出フェムト秒時間分解カー効果測定を行った。その結果、カロテノイドドープゲルがフェムト秒域で応答する大きな負の非線形性を持つこと、これらの非線形性発現のメカニズムは2光子過程によるものであることを明らかにした。 ・2.アゾベンゼンのH会合、J会合2分子膜を作製し、これらの電場変調吸収測定を行った。測定された電場変調スペクトルは、吸収スペクトルのエネルギー1階微分係数と相似な形をしており、1次のシュタルク効果によるものであることを明らかにした。 ・3.測定された電場変調吸収スペクトルとクラマ-ス・クロニヒ変換を用いた技法により、アゾベンゼン2分子膜の_χ^<(3)>の波長分散を240-500nmにおいて決定した。この結果、非共鳴域において、アゾベンゼン2分子膜は石英の10倍程度の_χ^<(3)>(H会合体:5.6×10^<-13>esu,J会合体:2.4×10^<-13>esu)を持つことが明らかとなり、高効率光変調デバイスへの応用が期待される。
  • 日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1996年 -1996年 
    代表者 : 森田 隆二
     
    本研究の目的は、長いπ共役系を有し、非線形光学特性が大きいとされるカロテノイドに注目し、その非線形特性のexcited-state enhancement、すなわち、実励起による非線形性の増大を生じさせ、非共鳴域で高速に応答する大きな非線形特性を得ることである。 本年度は、1.カロテノイド溶液の光ヘテロダイン検出フェムト秒時間分解光カー効果測定系の試作ならびにその測定、2.2光子励起過程を含むカロテノイドの非線形光学過程のメカニズムの解明を行った。 ●1.フェムト秒チタニウムサファイアレーザー(波長〜780nm,パルス幅〜90fs)を光源とする光ヘテロダイン検出フェムト秒時間分解カー効果測定系を試作し、高感度でカロテノイド(β,β-カロテン、カンタキサンチン)溶液の非線形光学特性の測定を行った。この結果、カロテノイドはフェムト秒に応答する大きな負の非線形性を持つことを明らかにした。 ●2.カロテノイドの大きな負の非線形性発現メカニズムを調べるため、フェムト秒時間分解カー効果の入力光強度依存性測定を行った。その結果から、カロテノイド溶液は、2光子過程に起因した、フェムト秒に応答する負の実効的3次非線形を持つことを見出した。また、この非線形性は、ポンプ光とプローブ光によるポピュレーショングレーティング効果によるものであることを明らかにした。これは、カロテノイドがexcited-state enhancementされうることを示唆する結果である。そこで、現在、チタニウムサファイアレーザーの光第2高調波を用いて、カロテノイドのexcited-stateenhancement実験に着手したところである。
  • 文部科学省:科学研究費補助金(一般研究(B), 基盤研究(B))
    研究期間 : 1994年 -1996年 
    代表者 : 山下 幹雄, 森田 隆二
     
    本研究は、周期可変なTHz繰り返しフェムト秒光パルス列による多様な分子凝縮系の特定振動量子状態制御をめざして、これに柔軟に対応できる光源としてのフェムト秒光波制御手法の開拓と、被制御対象として機能的物理的に意義ある分子系の探索とを目的として行われた。以下に成果を列挙する。(1)新しい近赤外から近紫外に渡る超広域帯(Δν=500〜600THz)準線形チャープパルス発生法の定量的提案。(2)フーリエ変換光学系・回折格子対・128チャンネル空間位相変調器からなる光波整形装置を用いた2.06THz繰り返しパルス列の発生。(3)フェムト秒時間分解干渉計法による、CS_2とその希釈液における2成分の非線形屈折率変化(n_<2//>(t)とn_<2⊥>(t))の高精度測定とその物理的起因の解明。(4)高時間分解縮退四光波混合分光による1- (3-thienyl) -3- (4-chlorophenyl) propene-1-one(TCPP)結晶・溶液および分子内電荷移動型分子である4-N,N- (dimethy1amino) -β-nitorostyrene(DEANST)溶液のフェムト秒域での3次非線形感受率の測定とその物理的起因の解明。(5)カロテノイド溶液のフェムト秒域での非共鳴Kerr応答特性の測定とその物理的起因の解明。(6)電場変調分光による、2分子アゾベンゼン膜、DEANS...
  • 文部科学省:科学研究費補助金(試験研究(B), 基盤研究(A))
    研究期間 : 1994年 -1996年 
    代表者 : 山下 幹雄, 土屋 裕, 上宮 崇文, 森田 隆二
     
    有限利得帯域幅を有するレーザーから発生できる最短パルス幅は、その帯域幅の逆数程度(半導体レーザーでは〜100fs)以下には狭くならない。本研究の目的は、(1)これ以下の短パルス化に必要な光パルス圧縮用高非線形導波素子を開発することである。さらに(2)現時点での世界最短パルスをブレークスルーする光パルスモノサイクル化手法を探索することも目的としている。以下に研究成果を列挙する。(1)GeO_2ドープシリカガラスシングルモードファイバーおよびEr:GeO_2ドープシリカガラスシングルモードファイバーのフェムト秒光パルス非線形伝搬実験を行い、それらの非線形屈折率n_2およびその応答時間T_Rがそれぞれn_2=2.4×n_<2,sio>2(石英ファイバーのn_2),T_R=1.8fsとn_2=3.6×n_<2,sio>2,T_R=2.1fsであることが明らかとなった。(2)ヘテロダイン検出方式高感度時間分解干渉法により、高PbOドープシリカガラスシングルモードファイバーのフェムト秒域での非線形屈折率n_2が9.2×n_<2,sio>2であることが明らかとなった。(3)30fsの非線形屈折率応答時間を有するDAN有機結晶シングルモードファイバーの、有限応答性によるパルス圧縮効率の低下は、非線形チャープを3次位相分散まで補償することによって防げることが明かとなった。(4)フェムト秒時間分...
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1995年 -1995年 
    代表者 : 岡 和彦, 森田 隆二
     
    本研究は、大きな非線形性を持つ有機材料の利点を生かしつつ、機械的なもろさを克服することのできる可能性のある有機・無機ゾル・ゲル薄膜を用いて非線形光学効果を利用した光変調デバイスを開発することである。 そこで、本年度は、有機材料としてカロテノイドに注目し、1.カロテノイドを用いた有機・無機ゾル・ゲルの作製、2.カロテノイド溶液の非線形光学特性の時間分解測定、3.カロテノイドを用いた有機・無機ゾル・ゲルの時間分解非線形光学特性の時間分解測定を行った。 ・1.テトラエトキシシラン、エタノールを用いて有機材料β,β-カロテンをドープした有機・無機ゾル・ゲルを初めて作製した。 ・2.カロテノイドであるβ,β-カロテン、カンタキサンチンの溶液に関して、光ヘテロダイン検出フェムト秒時間分解カー効果測定を行い、次のことを明らかにした。すなわち、これらのカロテノイド分子がフェムト秒域で応答する大きな負の非線形性を持つこと、これらの非線形性発現メカニズムは2光子過程によるものであること、である。 3.カロテノイドを用いた有機・無機ゾル・ゲルの光ヘテロダイン検出フェムト秒時間分解カー効果測定を行い、このゲルがフェムト秒時間域で応答する大きな負の非線形性を持つことを明らかにした。これにより、カロテノイドを用いた有機・無機ゾル・ゲルが、高効率光変調デバイス用材料として有望であるといえる。
  • 日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1994年 -1994年 
    代表者 : 森田 隆二
     
    有機材料DAN(4-(N,N-dimethylamino)-3-acetamidonitrobenzene)に注目し、除冷法・溶媒蒸発法により、バルク結晶の成長を行った。しかしながら、現在までのところ、この結晶は結晶性が悪く、ラマンスペクトル測定には成功しておらず、この方法によるDANの非線形屈折率の応答時間の評価は行えていない。 一方、DANを用いた有機単結晶コアファイバーをゾーンメルト法を用いて作製した。この有機結晶ファイバーを用いて、フェムト秒パルスレーザーパルスの非線形伝搬実験を行い、スペクトルが長波長側へシフトすることを見出した。この効果は、非線形屈折率の応答が瞬時ではなく、応答時間が有限であることに起因する。この結果を、非線形屈折率の応答時間効果を取り入れた非線形伝搬方程式を用いて解析し、有機材料DANの非線形屈折率の応答時間は約30fsであることを初めて見積もった。 さらに、このような非線形屈折率の応答時間効果のパルス圧縮効率への影響についての理論解析を行った。その結果、このような非線形屈折率の応答時間効果が存在しても、3次までの位相補償を行えば、効率を劣化させることなくパルス圧縮を行えること(たとえばDANファイバーにより100W,100fsの光パルスが約10fsに圧縮できること)を初めて明らかにした。
  • 文部科学省:科学研究費補助金(重点領域研究)
    研究期間 : 1993年 -1993年 
    代表者 : 山下 幹男, 山下 幹雄, 森田 隆二
     
    本研究の目的は、フェムト秒極限光パルスに高効率でスペクトルひろがりを与える自己位相変調素子を見いだすことである。そのために、本年度は以下の項目について研究を行った。1.2次、3次非線形性の大きい有機材料DAN(4-(N,N-dimethylamino)-3-acetamidonitrobenzene)を用いたファイバーを作製し、群速度分散が大きく非線形性も大きい材料を用いたファイバー中のフェムト秒光パルス伝搬についての実験的・理論的研究を行った。DANファイバー伝搬後のパルスには長波長側へのスペクトルシフトが見られ、これは自己位相変調を引き起こす原因となる非線形屈折率の応答速度の有限性に起因することを明らかにした。2.2次・3次分散、伝搬損失、初期周波数チャープ、自己急峻化の効果の他、正常分散域における非線形屈折率の応答時間効果を初めてとりこみ、DANファイバー中のフェムト秒パルスの伝搬およびパルス圧縮効率に関する理論解析を行った。その結果、非線形屈折率の応答時間効果が存在する場合でも、2・3次の位相分散補償を行えば、応答時間が存在しない場合と同程度のパルス圧縮効率が得られることを明らかにした。具体的には、DANファイバーを用いることによって、100W,100fsの光パルスを10fs程度に圧縮可能なことが示された。また、その結果、非線形性は大きいが、応答時間がある程度遅いと考...
  • 文部科学省:科学研究費補助金(重点領域研究)
    研究期間 : 1992年 -1992年 
    代表者 : 山下 幹男, 山下 幹雄, 森田 隆二
     
    本研究の目的は、フェムト秒極限光パルスに高効率でスペクトルひろがりを与える自己位相変調素子を見いだすことである。そのために、本年度は以下の項目について研究を行った。1.3次非線形光学定数の大きな物質の探索の一指針として、2次非線形光学定数と3次非線形光学定数の関係を明らかにした。この結果によれば、反転対弥性を持つ材料の3次非線形光学定数は、2次非線形光学定数の2乗に依存する。すなわち、2次非線形性の大きな3次非線形性をもち、今までに知られている2次非線形性の大きな材料が、3次非線形材料として、有望であることが示された。2.2次、3次非線形性の大きい有機材料DAN(4-(N,N-dimethylamino)-3-acetamidonitrobenzene)を用いたファイバーを作製し、群速度分散が大きく非線形性も大きい材料を用いたファイバー中のフェムト秒光パルス伝搬についての実験的・理論的研究を行った。ファイバー伝搬後のパルスには長波長側へのスペクトルシフトが見られ、これは自己位相変調を引き起こす原因となる非線形屈折率の応答速度が有限である起因すると考えらる。この応答時間の測定、応答時間効果がパルス圧縮に及ぼす影響について現在、検討を行っている。以上の項目を通じて、高効率自己位相変調素子の実現へ向けて重要な指針を示せたものと考える。
  • 極限時間域における非線形光学応答に関する研究、超広帯域フェムト秒光波の波形整形とその応用
    研究期間 : 1991年
  • ultrafast nonlinear optical phenomena, characterization and application of ultrashort optical pulses
    研究期間 : 1991年

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  • 応用物理学特別演習
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : 応用物理学、量子物理学、凝縮系物理学、応用工学、ナノサイエンス、ナノテクノロジー
  • 非線形光学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : 非線形分極,非線形感受率応答関数,非線形波動方程式,輻射と物質との相互作用,応答と分散,光パルスの非線形伝播,群速度,負の屈折率
  • 応用物理学特別研究
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : 応用物理学、量子物理学、凝縮系物理学、応用光学、ナノサイエンス、ナノテクノロジー
  • 非線形光学特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : 非線形分極,非線形感受率応答関数,非線形波動方程式,輻射と物質との相互作用,応答と分散,光パルスの非線形伝播,群速度,負の屈折率
  • インターンシップ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 想像的人材育成、実践的人材育成、就業体験、国内外インターンシップ
  • インターンシップⅠ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 想像的人材育成、実践的人材育成、就業体験、国内外インターンシップ
  • インターンシップⅡ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 想像的人材育成、実践的人材育成、就業体験、国内外インターンシップ
  • 創造工学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 社会的ニーズ、調査研究、研究発表、既存知識、課題解決法
  • 教科教育法(工業II)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 教育学部
    キーワード : 教員養成、工業、指導法
  • 科学英語演習
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 英語,読解,作文,英会話,プレゼンテーション,ディスカッション
  • 電磁気学Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 電荷、電場、電流、磁場、ポテンシャル、導体、双極子
  • 電磁気学演習Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 電荷、電場、電流、磁場、ポテンシャル、導体、双極子

大学運営

委員歴

  • 2021年11月 - 現在   外務省   パリ国際大学都市日本館館長選考委員
  • 2021年09月 - 現在   Frontiers in Photonics,   Associate Editor
  • 2018年04月 - 現在   Photonics Research (Optica, formerly Optical Society),   Associate Editor
  • 2017年04月 - 現在   Scientific Reports (Nature publishing group)   Editorial Board Member
  • 2014年04月 - 現在   応用物理学会   Applied Physics Express/ Japanese Journal of Applied Physics (APEX/JJAP) 編集委員
  • 2006年 - 現在   応用物理学会   日本光学会「光波シンセシス研究グループ」幹事   応用物理学会
  • 2023年 - 2024年   レーザー学会   プログラム委員
  • 2019年 - 2020年   レーザー学会   プログラム委員
  • 2017年04月 - 2019年03月   Maison du Japon, Cité Internationale Universitaire de Paris, Université de Paris,   Directeur
  • 2017年 - 2017年   Optical Society (of America)   Associate Editor, Special Issue, Optics Express
  • 2011年04月 - 2015年03月   応用物理学会   代議員   応用物理学会
  • 2011年   レーザー学会   プログラム委員   レーザー学会
  • 2009年   応用物理学会   日本光学会年次学術講演会 Optics & Photonics Japan 2009 プログラム委員   応用物理学会
  • 2007年 - 2008年   応用物理学会   応用物理学会誌編集委員   応用物理学会

社会貢献活動

  • 日本国外務省 パリ(フランス)国際大学都市日本館館長選考委員
    期間 : 2021年11月 - 現在
    役割 : 助言・指導
    主催者・発行元 : 日本国外務省
  • Directeur, Maison du Japon, Cité Internationale Universitaire de Paris (France)
    期間 : 2017年04月01日 - 2019年03月31日
    役割 : 助言・指導
    主催者・発行元 : 日本国外務省, パリ大学(フランス)

学術貢献活動

  • Associate Editor, Frontiers In Photonics
    期間 : 2021年09月 - 現在
    役割 : 企画立案・運営等
    種別 : 査読等
    主催者・責任者 : Frontiers (Open Acces Publisher)
  • Associate Editor, Photonics Research (Optica)
    期間 : 2018年04月 - 現在
    役割 : 企画立案・運営等
    種別 : 査読等
    主催者・責任者 : Optica Publishing Group
  • Editorial Board Member, Scientific Reports
    期間 : 2017年04月 - 現在
    役割 : 企画立案・運営等
    種別 : 査読等
    主催者・責任者 : Nature Publishing Grroup
  • 応用物理学会 フェロー
    期間 : 2016年09月 - 現在
    役割 : 審査・評価
    種別 : 学会・研究会等
    主催者・責任者 : 応用物理学会
  • Associate Editor, Applied Physics Express/ Japanese Journal of Applied Physics
    期間 : 2014年04月 - 現在
    役割 : 企画立案・運営等
    種別 : 学会・研究会等
    主催者・責任者 : 応用物理学会


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