Oct. 2021, 日本光学会, 第62回日本光学会光学論文賞　　　　　　　　　　　　　　　
ナノ構造光圧エンジニアリングによる光駆動ナノマシン

2020, レーザー学会, 第44回レーザー学会奨励賞　　　　　　　　　　　　　　　
プラズモニック光波制御デバイスとナノモーター応用
田中嘉人

2018, 文部科学大臣, 若手科学者賞　　　　　　　　　　　　　　　
局在プラズモン制御による超解像光マニピュレーションの研究
田中嘉人

2015, 東京大学 生産技術研究所, 生研弥生賞 最優秀　　　　　　　　　　　　　　　
デザインされたプラズモニックナノモーターによる運動駆動・制御
田中嘉人

2010, 北海道大学 電子科学研究所, 第39回松本・羽鳥奨励賞　　　　　　　　　　　　　　　
局在プラズモン場の高空間分解イメージング法の開発
田中嘉人

Unveiling orbital optical chirality through multipolar chiral light–matter interaction
Shun Hashiyada, An’an Wu, Yoshito Y. Tanaka
Optica, 13, 2, 353, 353, Optica Publishing Group, 17 Feb. 2026, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, Chiral light–matter interactions are central to optical spectroscopy and nanophotonics, yet they are conventionally understood as arising from electric–magnetic dipolar interference driven by light with spin angular momentum. Here, we show that optical chirality can also originate from the orbital angular momentum (OAM) of light, enabling chiral responses mediated by higher-order multipolar interactions. Using a single twisted gold nanorod dimer as a minimal chiral platform, we perform spatially and spectrally resolved measurements of chiral dichroism under tightly focused circularly polarized optical vortex beams carrying spin and orbital angular momenta of the same sign. We observe qualitatively distinct chiral responses at the vortex center and in the annular region of the beam. In particular, OAM-sign-dependent quadrupolar resonances emerge at the beam center, where conventional spin-induced optical chirality vanishes. Reciprocity tests and angular momentum dissipation analysis confirm that this response is a genuine chiral interaction dominated by orbital, rather than spin, angular momentum. These results establish the existence of a distinct form of optical chirality, referred to as orbital optical chirality, and open opportunities for probing multipolar chiral light–matter interactions beyond the dipolar paradigm.

Ambient-dependent reversal of unidirectional light scattering by metal–dielectric hybrid plasmonic nanoantenna
Shuto Watanabe, Ryuichi Ohta, Tsukasa Katayama, Yoshito Y. Tanaka
APL Photonics, 10, 12, 126114, AIP Publishing, 01 Dec. 2025, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, Unidirectional light scattering of plasmonic nanoantennas extends toward various nanophotonic applications, such as optical routers, molecular sensors, and light-driven actuators. The controllability of the direction of scattered light is crucial for those applications. So far, the large controllability enabling the reversal of the scattering direction has been achieved by tuning the wavelength and polarization of the incident light. Asymmetric dielectric nanostructures can also induce either unidirectional or bidirectional light scattering. However, such control methods relying on the incident light parameters and previous architecture limit the practical applicability of unidirectional light scattering, especially in sensing applications. Here, we propose and demonstrate a new hybrid architecture to control and reverse the unidirectional light scattering with respect to the ambient conditions through the integration of paired gold plasmonic nanorods and asymmetric dielectric shield. The dielectric shields selectively make certain nanorod less influential to the surrounding refractive index change, which results in the substantial controllability of direction of the scattered light with respect to the surrounding medium. Fourier imaging of the scattered light experimentally reveals the reversal of the scattering direction over a broad wavelength range. Numerical simulations reproduce the spectral response and directional scattering for various surrounding media, demonstrating a wide dynamic range and high sensitivity for the ambient refractive indices. These findings suggest that the nanoantenna can detect local molecular adsorption, leading to a compact and tunable platform for ambient-dependent optical devices with potential applications in nanophotonic sensing, reconfigurable photonics, and environment-adaptive light-driven nanomotors.

Optical trapping with gold nanoparticles for chiral crystallization: size-dependent enantioselectivity switch
Hao-Tse Su, Hiromasa Niinomi, An-Chieh Cheng, Yoshito Y. Tanaka, Keiji Sasaki, Teruki Suigiyama
Optical Manipulation and Structured Materials Conference 2025, 17, 17, SPIE, 05 Aug. 2025
International conference proceedings

Optical Activity Modulation in Chiral Metasurfaces via Structured Light
Paula L. Lalaguna, Shun Hashiyada, Nikolaj Gadegaard, Jörg B. Götte, Stephen M. Barnett, Kayn A. Forbes, Yoshito Y. Tanaka, Malcolm Kadodwala
Nano Letters, American Chemical Society (ACS), 05 Aug. 2025, [Peer-reviewed], [Corresponding author]
Scientific journal

Conservation law for angular momentum based on optical field derivatives: Analysis of optical spin-orbit conversion
Shun Hashiyada, Yoshito Y. Tanaka
Physical Review Research, 7, 2, American Physical Society (APS), 04 Jun. 2025, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, We present a theoretical framework for analyzing the loss of optical angular momentum (AM), including spin AM (SAM) and orbital AM (OAM) components, in light-matter interactions. Conventional SAM and OAM conservation laws rely on transverse field components, neglecting longitudinal fields and limiting applicability to a vacuum. Our approach defines optical AM using time derivatives of the electric and magnetic fields, yielding a gauge-invariant formulation that includes both transverse and longitudinal components and explicitly incorporates charge and current densities into SAM and OAM conservation laws. This enables a more complete description of AM dissipation in materials. We apply this framework to analyze spin-orbit conversion (SOC) in two scenarios: the scattering of circularly polarized (CP) Gaussian beams by a gold nanoparticle and focusing of CP Gaussian beams and linearly polarized optical vortex beams by a lens. The results show that SOC depends on particle size and polarization, with notable OAM loss in larger particles and CP Gaussian beam focusing. This framework enables the evaluation of previously overlooked SAM and OAM losses, providing a powerful tool for studying systems in which the analysis of AM losses is intrinsically important, such as chiral materials, as well as for designing photonic devices and exploring light-matter interactions at the nanoscale.

Published by the American Physical Society 2025

3-dimensional plasmonic nanomotors enabled by independent integration of optical pulling and lateral forces
G Serrera, YY Tanaka, P Albella
Nanophotonics, 2025, [Peer-reviewed]

Enantioselectivity switch in chiral crystallization using optical trapping with gold nanoparticles
Hao-Tse Su, Hiromasa Niinomi, An-Chieh Cheng, Yoshito Y. Tanaka, Keiji Sasaki, Teruki Sugiyama
Cell Reports Physical Science, 102310, 102310, Elsevier BV, Dec. 2024
Scientific journal

Π-shaped pixel pattern for shift multiplexing surface holograms in holographic data storage
Soki Hirayama, Ryushi Fujimura, Yoshito Y. Tanaka, Tsutomu Shimura
Optics Express, 32, 24, 42184, 42184, Optica Publishing Group, 04 Nov. 2024
Scientific journal, In this study, a method for shift multiplexing surface holograms was proposed for data storage systems. Shift multiplexing of surface holograms is inhibited by noise specific to Raman–Nath diffraction. We proposed a model to analyze the influence of noise. Subsequently, we proposed a method for noise suppression to arrange signal and reference pixels in a shape similar to the Greek letter “Π.” The proposed method is generally applicable to thin holograms in which Raman–Nath diffraction occurs. The effectiveness of noise suppression using the proposed method was experimentally demonstrated. We theoretically estimated that a shift multiplexing surface holographic data storage system using the proposed method could achieve a significantly higher data transfer rate than conventional optical discs while maintaining a comparable storage density.

Optical trapping-induced crystallization promoted by gold and silicon nanoparticles
Hao-Tse Su, Shao-Yuan Liu, Minoru Fujii, Hiroshi Sugimoto, Yoshito Y. Tanaka, Teruki Sugiyama
Photochemical & Photobiological Sciences, Springer Science and Business Media LLC, 30 Aug. 2024, [Peer-reviewed]
Scientific journal, Abstract

This study investigates the promotion of sodium chlorate (NaClO₃) crystallization through optical trapping, enhanced by the addition of gold nanoparticles (AuNPs) and silicon nanoparticles (SiNPs). Using a focused laser beam at the air–solution interface of a saturated NaClO₃ solution with AuNPs or SiNPs, the aggregates of these particles were formed at the laser focus, the nucleation and growth of metastable NaClO₃ (m-NaClO₃) crystals were induced. Continued laser irradiation caused these m-NaClO₃ crystals to undergo repeated cycles of growth and dissolution, eventually transitioning to a stable crystal form. Our comparative analysis showed that AuNPs, due to their significant heating due to higher photon absorption efficiency, caused more pronounced size fluctuations in m-NaClO₃ crystals compared to the stable behavior observed with SiNPs. Interestingly, the maximum diameter of the m-NaClO₃ crystals that appeared during the size fluctuation step was consistent, regardless of nanoparticle type, concentration, or size. The crystallization process was also promoted by using polystyrene nanoparticles, which have minimal heating and electric field enhancement, suggesting that the reduction in activation energy for nucleation at the particle surface is a key factor. These findings provide critical insights into the mechanisms of laser-induced crystallization, emphasizing the roles of plasmonic heating, particle surfaces, and optical forces.

Graphical abstract

Rapid modulation of left- and right-handed optical vortices for precise measurements of helical dichroism
Shun Hashiyada, Yoshito Y. Tanaka
Review of Scientific Instruments, 95, 5, AIP Publishing, 01 May 2024, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, Helical dichroism (HD), which is defined as the difference in optical absorption between chiral pairs of lights involving left-handed (LH) and right-handed (RH) optical vortices (OVs) carrying orbital angular momentum (OAM), is a promising way to characterize chiral materials. In the current major methods of OV generation using spatial light modulators (SLMs), the speed of OAM switching is typically as slow as 100 Hz, which is comparable to low-frequency noise, making precise chiral detection difficult. Here, we theoretically propose and experimentally demonstrate a rapid modulation of the LH and RH OVs at around 50 kHz. This modulation is achieved through a rapid modulation of circularly polarized lights carrying spin angular momentum (SAM), combined with a SAM–OAM conversion technique. We establish a theory not only for rapid OV modulation but also for HD measurements using the modulated OVs. We experimentally verify the theory using helical phase holograms drawn on a SLM as a pseudo-HD active sample. Our work addresses the limitations of current methods and offers a new avenue for precise HD measurements, paving the way for the development of sensitive chiral-optical spectroscopy techniques.

Radially Polarized Second-Harmonic Generation from a Single- Element Nanoantenna via Dark Plasmon Coupling of Nonlinear Polarization
Tomoya Kimura, Yoshito Y. Tanaka, Tsutomu Shimura
ACS PHOTONICS, Oct. 2022, [Last author, Corresponding author]
English, Scientific journal

Complex amplitude modulated holographic data storage based on one phase spatial light modulator
Jianying Hao, Xiao Lin, Soki Hirayama, Ryushi Fujimura, Yoshito Tanaka, Xiaodi Tan, Tsutomu Shimura
Optics InfoBase Conference Papers, 2022
International conference proceedings

Unidirectional emission of phase-controlled second harmonic generation from a plasmonic nanoantenna
Yoshito Tanaka
Nanophotonics, 10, 18, 4601, 4609, 02 Dec. 2021, [Peer-reviewed], [Lead author, Corresponding author]
Scientific journal

Giant chiroptical response of twisted metal nanorods due to strong plasmon coupling
An'an Wu, Yoshito Y. Tanaka, Tsutomu Shimura
APL Photonics, 6, 12, 126104, 126104, {AIP} Publishing, 01 Dec. 2021, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Plasmonic linear nanomotor using lateral optical forces
Yoshito Y. Tanaka, Pablo Albella, Mohsen Rahmani, Vincenzo Giannini, Stefan A. Maier, Tsutomu Shimura
SCIENCE ADVANCES, 6, 45, Nov. 2020, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Interactions Between Epitaxial Graphene Grown on the Si- and C-Faces of 4H-SiC Investigated Using Raman Imaging and Tip-Enhanced Raman Scattering
Shohei Uemura, Sanpon Vantasin, Yasutaka Kitahama, Yoshito Yannick Tanaka, Toshiaki Suzuki, Daichi Doujima, Tadaaki Kaneko, Yukihiro Ozaki
APPLIED SPECTROSCOPY, 74, 11, 1384, 1390, Nov. 2020, [Peer-reviewed]
English, Scientific journal

Continuity equation for spin angular momentum in relation to optical chirality
An'an Wu, Yoshito Y. Tanaka, Ryoma Fukuhara, Tsutomu Shimura
PHYSICAL REVIEW A, 102, 2, Aug. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Enhanced Surface Plasmon Resonance Wavelength Shifts by Molecular Electronic Absorption in Far- and Deep-Ultraviolet Regions
Ichiro Tanabe, Yoshito Y. Tanaka, Koji Watari, Wataru Inami, Yoshimasa Kawata, Yukihiro Ozaki
SCIENTIFIC REPORTS, 10, 1, Jun. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal

High noise margin decoding of holographic data page based on compressed sensing
Jinpeng Liu, Le Zhang, Anan Wu, Yoshito Tanaka, Masanobu Shigaki, Tsutomu Shimura, Xiao Lin, Xiaodi Tan
OPTICS EXPRESS, 28, 5, 7139, 7151, Mar. 2020, [Peer-reviewed]
English, Scientific journal

Plasmon-hybridization-induced optical torque between twisted metal nanorods
An'an Wu, Yoshito Y. Tanaka, Tsutomu Shimura
OPTICS EXPRESS, 28, 2, 2398, 2410, Jan. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Transverse optical torque induced by localized surface plasmons
Ryoma Fukuhara, Yoshito Y. Tanaka, Tsutomu Shimura
PHYSICAL REVIEW A, 100, 2, Aug. 2019, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Far- and Deep-Ultraviolet Surface Plasmon Resonance Sensor
Ichiro Tanabe, Yoshito Y. Tanaka
CHEMICAL RECORD, 19, 7, 1210, 1219, Jul. 2019, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Theoretical Study of a Surface Collinear Holographic Memory
Soki Hirayama, Ryushi Fujimura, Shinsuke Umegaki, Yoshito Y. Tanaka, Tsutomu Shimura
PHOTONICS, 6, 2, Jun. 2019, [Peer-reviewed]
English, Scientific journal

Soft trapping lasts longer: Dwell time of a Brownian particle varied by potential shape
Itsuo Hanasaki, Takahiro Nemoto, Yoshito Y. Tanaka
PHYSICAL REVIEW E, 99, 2, Feb. 2019, [Peer-reviewed], [Last author]
English, Scientific journal

Plasmonic-Diffractive Hybrid Sensors Based on a Gold Nanoprism Array
Kazutaka Akiyoshi, Yoshito Y. Tanaka, Takuya Ishida, Tsutomu Shimura, Tetsu Tatsuma
ACS APPLIED NANO MATERIALS, 1, 11, 5994, 5999, Nov. 2018, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Launching and Control of Graphene Plasmons by Nanoridge Structures
Sanpon Vantasin, Yoshito Y. Tanaka, Tsutomu Shimura
ACS PHOTONICS, 5, 3, 1050, 1057, Mar. 2018, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Fast non-interferometric iterative phase retrieval for holographic data storage
Xiao Lin, Yong Huang, Tsutomu Shimura, Ryushi Fujimura, Yoshito Tanaka, Masao Endo, Hajimu Nishimoto, Jinpeng Liu, Yang Li, Ying Liu, Xiaodi Tan
OPTICS EXPRESS, 25, 25, 30905, 30915, Dec. 2017, [Peer-reviewed]
English, Scientific journal

Aluminum Film Thickness Dependence of Surface Plasmon Resonance in the Far- and Deep-ultraviolet Regions
Ichiro Tanabe, Yoshito Y. Tanaka, Koji Watari, Taras Hanulia, Takeyoshi Goto, Wataru Inami, Yoshimasa Kawata, Yukihiro Ozaki
CHEMISTRY LETTERS, 46, 10, 1560, 1563, Oct. 2017, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Far- and deep-ultraviolet surface plasmon resonance sensors working in aqueous solutions using aluminum thin films
Ichiro Tanabe, Yoshito Y. Tanaka, Koji Watari, Taras Hanulia, Takeyoshi Goto, Wataru Inami, Yoshimasa Kawata, Yukihiro Ozaki
SCIENTIFIC REPORTS, 7, Jul. 2017, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Tridirectional Polarization Routing of Light by a Single Triangular Plasmonic Nanoparticle
Yoshito Y. Tanaka, Tsutomu Shimura
NANO LETTERS, 17, 5, 3165, 3170, May 2017, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Analysis of blinking from multicoloured SERS-active Ag colloidal nanoaggregates with poly-L-lysine via truncated power law
Yasutaka Kitahama, Takuji Nagahiro, Yoshito Tanaka, Tamitake Itoh, Yukihiro Ozaki
JOURNAL OF RAMAN SPECTROSCOPY, 48, 4, 570, 577, Apr. 2017, [Peer-reviewed]
English, Scientific journal

Direct optical measurements of far- and deep-ultraviolet surface plasmon resonance with different refractive indices
Ichiro Tanabe, Yoshito Y. Tanaka, Takayuki Ryoki, Koji Watari, Takeyoshi Goto, Masakazu Kikawada, Wataru Inami, Yoshimawa Kawata, Yukihiro Ozaki
OPTICS EXPRESS, 24, 19, 21886, 21896, Sep. 2016, [Peer-reviewed], [Corresponding author]
English, Scientific journal

3D SERS Imaging Using Chemically Synthesized Highly Symmetric Nanoporous Silver Microparticles
Sanpon Vantasin, Wei Ji, Yoshito Tanaka, Yasutaka Kitahama, Mengfan Wang, Kanet Wongravee, Harnchana Gatemala, Sanong Ekgasit, Yukihiro Ozaki
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 55, 29, 8391, 8395, Jul. 2016, [Peer-reviewed]
English, Scientific journal

Side-illuminated tip-enhanced Raman study of edge phonon in graphene at the electrical breakdown limit
Yoshito Okuno, Sanpon Vantasin, In-Sang Yang, Jangyup Son, Jongill Hong, Yoshito Yannick Tanaka, Yasushi Nakata, Yukihiro Ozaki, Nobuyuki Naka
APPLIED PHYSICS LETTERS, 108, 16, Apr. 2016
English, Scientific journal

Tip-Enhanced Raman Scattering of Local Nanostructure on Large Sheet and Microisland Epitaxial Graphene Grown on 4H–SiC (0001)
Sanpon Vantasin, Shohei Uemura, Yoshito Tanaka, Daichi Doujima, Tadaaki Kaneko, Yukihiro Ozaki
ACS Symposium Series, 227, 245, American Chemical Society, Jan. 2016
In book

3D SERS imaging based on chemically-synthesized highly-symmetric nanoporous silver microparticles
Yukihiro Ozaki, Sanpon Vantasin, Wei Ji, Yoshito Tanaka, Yasutaka Kitahama, Kanet Wongrawee, Sanong Ekgasit
NANOIMAGING AND NANOSPECTROSCOPY IV, 9925, 2016
English, International conference proceedings

Tip-enhanced Raman spectroscopy of nanostructures on epitaxial graphene and graphene microisland
Sanpon Vantasin, Toshiaki Suzuki, Yoshito Tanaka, Yasutaka Kitahama, Shohei Uemura, Doujima Daichi, Tadaaki Kaneko, Yukihiro Ozaki
NANOIMAGING AND NANOSPECTROSCOPY IV, 9925, 2016
English, International conference proceedings

Development of far- and deep-ultraviolet surface plasmon resonance (SPR) sensor using aluminum thin film
Ichiro Tanabe, Yoshito Y. Tanaka, Takayuki Roki, Koji Watari, Takeyoshi Goto, Masakazu Kikawada, Wataru Inami, Yoshimasa Kawata, Yukihiro Ozaki
UV AND HIGHER ENERGY PHOTONICS: FROM MATERIALS TO APPLICATIONS, 9926, 2016
English, International conference proceedings

Nanoscale Color Sorting of Surface Plasmons in a Double-Nanogap Structure with Multipolar Plasmon Excitation
Yoshito Y. Tanaka, Masaya Komatsu, Hideki Fujiwara, Keiji Sasaki
NANO LETTERS, 15, 10, 7086, 7090, Oct. 2015, [Peer-reviewed], [Lead author]
English, Scientific journal

Two-photon excited fluorescence from a pseudoisocyanine-attached gold tip via a plasmonic-photonic hybrid system
Fang Ren, Hideaki Takashima, Yoshito Tanaka, Hideki Fujiwara, Keiji Sasaki
OPTICS EXPRESS, 23, 17, 21730, 21740, Aug. 2015, [Peer-reviewed]
English, Scientific journal

Characterization of SiC-grown epitaxial graphene microislands using tip-enhanced Raman spectroscopy
Sanpon Vantasin, Yoshito Tanaka, Shohei Uemura, Toshiaki Suzuki, Yasunori Kutsuma, Daichi Doujima, Tadaaki Kaneko, Yukihiro Ozaki
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17, 43, 28993, 28999, 2015, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Enantioselective Discrimination of Alcohols by Hydrogen Bonding: A SERS Study
Yue Wang, Zhi Yu, Wei Ji, Yoshito Tanaka, Huimin Sui, Bing Zhao, Yukihiro Ozaki
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 53, 50, 13866, 13870, Dec. 2014
English, Scientific journal

Tip-Enhanced Raman Scattering of the Local Nanostructure of Epitaxial Graphene Grown on 4H-SiC (000(1)over-bar)
Sanpon Vantasin, Ichiro Tanabe, Yoshito Tanaka, Tamitake Itoh, Toshiaki Suzuki, Yasunori Kutsuma, Koji Ashida, Tadaaki Kaneko, Yukihiro Ozaki
JOURNAL OF PHYSICAL CHEMISTRY C, 118, 44, 25809, 25815, Nov. 2014
English, Scientific journal

Optical nanomanipulation using nanoshaped plasmonic fields
Keiji Sasaki, Shutaro Ishida, Kyosuke Sakai, Yoshito Tanaka
JSAP-OSA Joint Symposia, JSAP 2014, Optical Society of America (OSA), 01 Sep. 2014
English, International conference proceedings

Efficient optical coupling into a single plasmonic nanostructure using a fiber-coupled microspherical cavity
Hideaki Takashima, Kazutaka Kitajima, Yoshito Tanaka, Hideki Fujiwara, Keiji Sasaki
PHYSICAL REVIEW A, 89, 2, 021801, 021801, Feb. 2014, [Peer-reviewed]
English, Scientific journal

Two-photon excited fluorescence from a pseudoisocyanine-attached gold-coated tip via a thin tapered fiber under a weak continuous wave excitation
Fang Ren, Hideaki Takashima, Yoshito Tanaka, Hideki Fujiwara, Keiji Sasaki
OPTICS EXPRESS, 21, 23, 27759, 27769, Nov. 2013
English, Scientific journal

Near-field optical response of periodically arrayed plasmonic nanogap antennas
Kyosuke Sakai, Kensuke Nomura, Yoshito Tanaka, Keiji Sasaki
JOURNAL OF APPLIED PHYSICS, 114, 2, Jul. 2013
English, Scientific journal

Nanostructured Potential of Optical Trapping Using a Plasmonic Nanoblock Pair
Yoshito Tanaka, Shogo Kaneda, Keiji Sasaki
NANO LETTERS, 13, 5, 2146, 2150, May 2013, [Peer-reviewed], [Lead author]
English, Scientific journal

Direct imaging of localized fields in a gold nanostructure using a scattering-type near-field microscope
Hideki Fujiwara, Yoshito Tanaka, Keiji Sasaki
2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR), 2013, [Peer-reviewed]
English, International conference proceedings

Nonlinear phenomena from a PIC-attached gold tip using a plasmonic-whispering gallery mode hybrid
Fang Ren, Hideaki Takashima, Yoshito Tanaka, Hideki Fujiwara, Keiji Sasaki
NANOENGINEERING: FABRICATION, PROPERTIES, OPTICS, AND DEVICES X, 8816, 2013, [Peer-reviewed]
English, International conference proceedings

Nanopattern Fabrication of Gold on Hydrogels and Application to Tunable Photonic Crystal
Naonobu Shimamoto, Yoshito Tanaka, Hideyuki Mitomo, Ryuzo Kawamura, Kuniharu Ijiro, Keiji Sasaki, Yoshihito Osada
ADVANCED MATERIALS, 24, 38, 5243, 5248, Oct. 2012
English, Scientific journal

Nanoscale interference patterns of gap-mode multipolar plasmonic fields
Yoshito Tanaka, Akio Sanada, Keiji Sasaki
SCIENTIFIC REPORTS, 2, Oct. 2012, [Peer-reviewed], [Lead author]
English, Scientific journal

Efficient optical trapping using small arrays of plasmonic nanoblock pairs
Yoshito Tanaka, Keiji Sasaki
APPLIED PHYSICS LETTERS, 100, 2, Jan. 2012, [Peer-reviewed]
English, Scientific journal

Confinement of Photopolymerization and Solidification with Radiation Pressure
Syoji Ito, Yoshito Tanaka, Hiroyuki Yoshikawa, Yukihide Ishibashi, Hiroshi Miyasaka, Hiroshi Masuhara
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 133, 37, 14472, 14475, Sep. 2011, [Peer-reviewed]
English, Scientific journal

Optical trapping through the localized surface-plasmon resonance of engineered gold nanoblock pairs
Yoshito Tanaka, Keiji Sasaki
OPTICS EXPRESS, 19, 18, 17462, 17468, Aug. 2011, [Peer-reviewed], [Lead author]
English, Scientific journal

Direct imaging of nanogap-mode plasmon-resonant fields
Yoshito Tanaka, Hiroyasu Ishiguro, Hideki Fujiwara, Yukie Yokota, Kosei Ueno, Hiroaki Misawa, Keiji Sasaki
OPTICS EXPRESS, 19, 8, 7726, 7733, Apr. 2011, [Peer-reviewed], [Lead author]
English, Scientific journal

Selection and transfer of individual plasmon-resonant metal nanoparticles
Yoshito Tanaka, Keiji Sasaki
APPLIED PHYSICS LETTERS, 96, 5, Feb. 2010, [Peer-reviewed], [Lead author]
English, Scientific journal

Laser-induced self-assembly of silver nanoparticles via plasmonic interactions
Yoshito Tanaka, Hiroyuki Yoshikawa, Tamitake Itoh, Mitsuru Ishikawa
OPTICS EXPRESS, 17, 21, 18760, 18767, Oct. 2009, [Peer-reviewed], [Lead author]
English, Scientific journal

Direct Observation of Localized Fields in Nanogaps between Metal Particles Using a Scattering-Type Near-Field Microscope
Hideki Fujiwara, Yoshito Tanaka, Hiroyasu Ishiguro, Atsushi Saito, Keiji Sasaki
APPLIED PHYSICS EXPRESS, 2, 10, 102002, Oct. 2009, [Peer-reviewed]
English, Scientific journal

Surface Enhanced Raman Scattering from Pseudoisocyanine on Ag Nanoaggregates Produced by Optical Trapping with a Linearly Polarized Laser Beam
Yoshito Tanaka, Hiroyuki Yoshikawa, Tamitake Itoh, Mitsuru Ishikawa
JOURNAL OF PHYSICAL CHEMISTRY C, 113, 27, 11856, 11860, Jul. 2009, [Peer-reviewed], [Lead author]
English, Scientific journal

Laser microfixation of highly ordered J aggregates on a glass substrate
Yoshito Tanaka, Hiroyuki Yoshikawa, Tsuyoshi Asahi, Hiroshi Masuhara
APPLIED PHYSICS LETTERS, 91, 4, Jul. 2007, [Lead author]
English, Scientific journal

SiC(0001)C面上単層グラフェンアイランドのチップ増強ラマン分光解析
上村奨平, VANTASIN Sanpon, 久津間保徳, 田中嘉人, 北濱康孝, 金子忠昭, 尾崎幸洋, 分子科学討論会講演プログラム&要旨(Web), 9th, 2015

Super-Resolution Optical Trapping with Control of Localized Plasmonic Fields
笹木 敬司, 田中 嘉人, レーザー研究 = The review of laser engineering : レーザー学会誌, 42, 10, 761, 765, Oct. 2014
レーザー学会, Japanese

ナノ構造が拓くマクロな物体の光マニピュレーション　　　　　　　　　　　　　　　
創発的研究支援事業
Apr. 2022 - Mar. 2029
田中嘉人
科学技術振興機構, 東京大学, Principal investigator

ナノ構造光圧アクチュエータの開拓と量子共振器光バネ振動子の創出
科学研究費助成事業
01 Apr. 2024 - 31 Mar. 2027
田中 嘉人, 松本 伸之, 蓑輪 陽介
日本学術振興会, 基盤研究(A), 北海道大学, 24H00424

Nonlinear chiral optical responses by helical light fields
Grants-in-Aid for Scientific Research Grant-in-Aid for Transformative Research Areas (A)
Jun. 2022 - Mar. 2027
余越 伸彦, 田中 嘉人
Japan Society for the Promotion of Science, Grant-in-Aid for Transformative Research Areas (A), Osaka Metropolitan University, Coinvestigator, 22H05132

表面分子吸着に応じてパッシブ制御可能なプラズモニックナノモーターの創出
科学研究費助成事業 基盤研究(B)
Apr. 2019 - Mar. 2022
田中 嘉人
金属ナノ構造表面近傍の分子の状態や化学反応等に応じて自律的に運動を制御する光駆動ナノモーターの創出を目指し、分子とナノ構造の相互作用に伴う局在プラズモン共鳴変化により光圧が高感度に応答する金属ナノ構造体を研究した。特に、本年度は、シミュレーションによるナノ構造の設計を集中して行った。
長さの異なる２本のナノロッドは、局在プラズモン間の位相差により指向性側方光散乱を生じる。この反作用として、散乱方向と逆向きにナノロッドペアに面内光圧が働く。この光圧を駆動力とするナノモーターを基に設計を行った。この光圧は局在プラズモン共鳴に基づくものであるため、周辺屈折率変化に応じて力の大きさが変化する。今回、片方のナノロッドのみをSiO2で囲んだナノ構造を考えた。つまり、周辺屈折率変化に対して、SiO2で囲んだナノロッドのプラズモン共鳴は変化しない。これにより、周辺屈折率の変化に対するロッド間のプラズモン位相差の変化が増大すると期待される。設計したナノ構造の光散乱パターンを電磁場シミュレーションにより解析したところ、周辺屈折率に対する散乱の指向性が、SiO2を囲んでない場合と比較して大きく変化することが確認された。また面白いことに、SiO2で囲んだロッドのプラズモン共鳴が変化しないため、周辺屈折率を大きくしていくと位相差の逆転が生じ、指向性散乱の方向が逆方向に転ずる様子が見られた。そこで、面内光圧をMaxwell応力法によって計算したところ、周辺屈折率に対して力の大きさが変化するだけでなく、力方向が逆転することも確認できた。従って、周辺屈折率に応じて運動方向を自律的に制御するナノモーターが期待される。
日本学術振興会, 基盤研究(B), 東京大学, Principal investigator, 19H02533

光駆動マイクロマシンによる単一量子ドットに働く光圧計測法の開発
科学研究費助成事業 新学術領域研究(研究領域提案型)
01 Apr. 2019 - 31 Mar. 2021
田中 嘉人
光トラップしたマイクロプラットフォーム（MPF）を用いて、ナノ粒子に働く光圧・光トルクを計測する方法の開発を引き続き行った。具体的には、MPFの作製プロセス、特に薄膜形成プロセスの真空度等を見直すことでサンプル成功率を、当初の10%から100%近くに向上させた。また、MPFの界面で働く光圧や内部多重反射による影響がナノ粒子に働く光圧の精密計測において致命的なノイズになることを突き止め、この問題を解決するためにMPFと周辺媒質の屈折率をマッチングしてMPFの光捕捉・位置計測をできるようにした。これまで用いてきたMPFのパターンマッチングによる位置測定から、MPFに埋め込んだ４つの金ナノ粒子からの散乱光の非点収差による3次元位置測定に変更することで分解能を大幅に向上させた。これにより、MPFの位置(x, y, z)と回転(θx, θy, θz)の3次元測定を行うことで、~1.5fNと~2.0fNnmの感度・分解能でナノ粒子に働く光圧(Fx, Fy, Fz)と光トルク(Tθx, Tθy, Tθz)を計測できることを明らかにした。
本手法を用いて新学術領域で活発に議論されているキラルナノ物質に働く光圧・光トルクを明らかにするため、2本の金ナノロッドから構成される3次元キラルナノ構造を10nmの空間分解能で距離を制御して作製するプロセス（電子線ビームリソグラフィの２重露光とドライエッチング）を開発した。ナノロッド間の距離とねじれ角度を最適化することで、自然界の分子の1000倍大きい1.03のg値(キラリティーの指標)を実験と理論により実現した。
日本学術振興会, 新学術領域研究(研究領域提案型), 東京大学, 19H04670

Up-conversion high spatial resolution measurement of the wavevector of mid-infrared graphene plasmon
Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)
29 Jun. 2018 - 31 Mar. 2020
Tanaka Yoshito
In this study, we developed new approach for super-resolution imaging of wavevector in mid-infrared graphene plasmon via analysis of optical trapping potential for a nanoparticle. During the period, we constructed the system that is transparent in the region between visible and mid-IR and realized up-conversion measurement of infrared optical force on nanoparticles from the analysis of the potential analysis. Furthermore, we revealed that graphene-nanoridge structures allows launching and controlling their plasmons. In addition, we demonstrated, for the first time, Raman chiral activity on twisted stack graphene.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Exploratory), The University of Tokyo, 18K18992

マイクロ粒子の光捕捉ポテンシャル解析を活用したナノ物質への光圧測定法の開発
科学研究費助成事業 新学術領域研究(研究領域提案型)
01 Apr. 2017 - 31 Mar. 2019
田中 嘉人
本研究は、ナノ物質に働く光圧のポテンシャル解析における問題点（1. 短い光捕捉時間、2. 微弱なプローブ信号）を解決するために、マイクロ粒子を対象とした光捕捉ポテンシャル解析を活用することにより、ナノ物質に作用するフェムトニュートンオーダーの光圧を精密測定する手法を世界に先駆けて開発するものである。
本年度は、昨年度に開発した光駆動マイクロマシンによるナノ物質に働く光圧計測法を発展させ、さらなる力感度向上させるため、アクティブフィードバックによる光捕捉ポテンシャル制御法を開発した。具体的には、ポテンシャル深さが数kTになる低い光強度でマイクロプラットフォーム（MPF）を捕捉し、低いバネ定数（高い力検出感度）のポテンシャルを形成した。次に、CMOSカメラで撮像したMPFの位置をマルチスレッド処理によりリアルタイムに高速解析し、設定した捕捉領域から外れる場合に、電気光学素子（EOM）で光強度を上げてMPFに働く捕捉力を一時的に増大し、捕捉領域に戻すというフィードバックを行った。このようなMPFが感じる光場を高速に制御するシステムを開発し、従来法では難しかった高い力感度と長時間捕捉（高SN比）を併せ持つ捕捉ポテンシャルを実現し、原理的には10fN程度の力計測が可能であることが見積もられた。また、このフィードバックによるポテンシャル形状の制御を有限差分法でシミュレーションし、実験結果から光圧を正確に解析する方法を検討した。さらに、本手法の光圧計測における有効性を示すために、従来法では難しかったナノロッドに働く光トルクの定量計測を行った。現在のことろ、ナノロッドを中心に配置したMPFの光捕捉ポテンシャル計測に成功し、170pNnm/mradのバネ定数で30pNnm以上の分解能が得られることを明らかにした。
日本学術振興会, 新学術領域研究(研究領域提案型), 東京大学, 17H05462

局在プラズモン制御による光駆動ナノモーター創出　　　　　　　　　　　　　　　
戦略的創造研究推進事業 「さきがけ」
Dec. 2015 - Mar. 2019
田中嘉人
科学技術振興機構, Principal investigator

Highly-efficient two-photon reaction processes using entanglement of localized plasmons
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
01 Apr. 2011 - 31 Mar. 2015
SASAKI Keiji, FUJIWARA Hideki, TANAKA Yoshito
Utilizing the synergistic effect of the plasmonic enhancement and temporal entangled photons in plasmonic metal nanostructures, we have developed elemental technologies for the realization of highly-efficient two-photon reaction process. We performed theoretical evaluations of enhanced electric fields and found that further electric field enhancement could be expected by the periodic array of gold nano-gap structures. Then, we experimentally examined that two-photon excited fluorescence was enhanced by at least 5 order of magnitude in the periodic gold nanostructure. Furthermore, using a tapered-fiber coupled microsphere, we also developed a plasmonic-photonic hybrid system for highly-efficient plasmon excitation, which can focus an incident light to a small gold nanostructure with 100% efficiency. To experimentally verify the efficient plasmon excitation, we succeeded in the observation of SHG and two-photon excited fluorescence under a weak CW excitation (a few kW/cm2).
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 23246016

プラズモニックアレイによるナノ空間光マニピュレーション
科学研究費助成事業 特別研究員奨励費
2012 - 2014
田中 嘉人
プラズモン共鳴を励振する際に生じる局所温度上昇は、微粒子のプラズモントラッピングにおける安定性を考える上で極めて重要であることがら、本年度は1. 熱伝導性の高い基板をヒートシンクとして用いる方針と、2. プラズモニックナノ構造に代わって、高屈折率を持ち誘電体の虚数が小さい半導体ナノ構造を用いる方針で課題克服に向けて取り組んで来た。1. について具体的には、熱伝導性がガラスの数十倍高いサファイアを基板として用い、これまでと同じように電子線ビームリソグラフィ/リフトオフ法によってナノ構造を作製し、SEMやAFMによって形状を、顕微分光によりプラズモン共鳴特性を、近接場顕微鏡により光局在場分布を評価し、シミュレーションで用いたモデルと極めて近い形状・特性を得る事ができた。サファイア基板上金ナノブロックペアを用いて100nm粒子のプラズモントラッピングをしたところ、ガラス基板を用いた場合と比べナノ粒子の位置揺らぎが1/5まで抑えることが可能であることを明らかにした。次に、2. についてSiやGaPのナノブロックペアを対象に可視光照射に伴う局所温度上昇を計算によって見積もったところ、Siナノ構造については金を使った場合に比べ1/100の温度上昇、GaPナノ構造については誘電率の虚部がゼロのため全く温度上昇しないということを見出した。SiやGaPナノ構造で生じる局在場が微粒子捕捉で働く放射圧をMaxwell応力法によって計算したところ、金を使った場合にくらべ1/3程度になることがわかり、金ナノ構造を使った場合より3倍以上の光照射をすれば放射圧の大きさを同程度に保ちながら、局所温度上昇の影響をかなり抑えることができる可能性を示す事ができた。
日本学術振興会, 特別研究員奨励費, 北海道大学, 12J03862

Radiation Pressure Cooling With Localized Surface Plasmon
Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
2011 - 2012
SASAKI Keiji, FUJIWARA Hideki, TANAKA Yoshito
We have theoretically and experimentally investigated radiation pressure induced by localized surface plasmon (LSP) of metal nano-gap structures, and analyzed the strength and spatial distribution of the optical force exerted on nanometer-sized particles and molecules under thermal motions. We showed that the nanoscale spatial profiles of the LSP fields within the nano-gap exhibit complicated fine structures, rather than single peaks. The nanopatterns are formed by interferences of dipolar, quadrupolar, and higher-order multipolar plasmonic modes. In addition, we developed the measurement system for quantitatively analyzing the radiation pressure exerted on nanoparticles. The experimental results demonstrated that the force strength is enhance by 3 order of magnitude compared to that with conventional far-filed trapping. We also succeeded in observation of two-dimensional trapping potentials, which is the first demonstration of super-resolution optical trapping.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 23656039

1分子光捕捉を目指したプラズモニックナノ構造の作製
科学研究費補助金(若手研究(B))
2009 - 2011
田中嘉人
金属ナノ構造に光を照射すると、金属構造中に含まれる自由電子が光エネルギーを吸収することにより集団振動(局在表面プラズモン)を始め、その結果金属ナノ構造の表面近傍のナノ領域に極めて高い光局在場が生じる。この光局在場では極めて大きな光放射圧(電場勾配力)が分子やナノ物質に働くことが予想される。そこで、時間領域差分法(FDTD)を用いて金属ナノ構造近傍の電場分布を計算し、光放射圧が働く領域と場所毎に働く光放射圧の強さを見積もった。その結果、1.光増強度の高い構造は光の局在特性も高く一度光捕捉した分子の閉じ込めは大きい一方、光放射圧が働く領域が極めて小さくなる、2.光増強度の低い構造は光の局在性も低く、光放射圧が働く領域は広くなるが分子に働く光放射圧の大きさは小さくなることがわかった。そこで、金ナノダイマー構造のギャップ距離が小さくかつその距離を緩やかに変化する金ナノ構造を提案した。提案した金属ナノ構造を電子線ビームリソグラフィで作製するにあたり、電子線描画の条件、現像条件、金属蒸着条件、リフトオフ条件等の最適化を行った。現在の所高い再現性は未だ得られないものの2ナノメートル以下の精度で金ナノ構造のギャップを作製することに成功している。広い入射波長に対応するために、多様なサイズのナノ構造作製条件も模索している。来年度はFDTDを用いて構造の最適化を進めると共に電子線ビームリソグラフィ...
文部科学省, 若手研究(B), 北海道大学, Principal investigator, Competitive research funding, 21710090

光圧ポテンシャルにより分子レベルの秩序構造を制御したJ会合体の作製・配列
科学研究費助成事業 特別研究員奨励費
2006 - 2008
田中 嘉人
これまでの研究で、光圧ポテンシャルが働くレーザー集光位置において、J会合体の核形成が促進されること、核形成したJ会合体は自然析出するJ会合体に比べ分子の配向秩序が高く非線形光学材料として優れていることなどを明らかにしてきた。つまり、光圧ポテンシャルによりJ会合体の形成や分子配列が制御できることがわかってきた。次のステップとして、本年度はJ会合体にかわり銀ナノ粒子凝集体に注目した。銀ナノ粒子凝集体もJ会合体同様、ナノ粒子の配列構造によって光圧ポテンシャルエネルギーが大きく変化する。以下に本研究成果の要旨を示す。
1.レーザー集光位置で形成する銀ナノ粒子凝集体の凝集構造を、粒子間のプラズモニック相互作用によって直線偏光と円偏光で制御できることを明らかにした。
2.直線偏光したレーザー集光位置では1次元状に銀ナノ粒子が配列し、電場の偏光方向に長軸が配向することを見出した。
3.2の銀ナノ粒子凝集体は照射レーザー光波長において強いプラズモン共鳴を示し、吸着分子の表面増強ハイパーラマン散乱を測定することに成功した。
4.レーザー集光位置で形成した銀ナノ粒子凝集体は、強い電場増強サイト(いわゆるホットスポット)に分子を光捕捉できることを実証した。
本研究成果は、分子だけでなく金属ナノ粒子の配列構造も光圧ポテンシャルにより制御できることを示すものであり、光圧ポテンシャル効果の高い一般性を示すと共にその有用性を示すことにも成功した。
日本学術振興会, 特別研究員奨励費, 06J09148