Researcher Database

Keiji Sasaki
Research Institute for Electronic Science Photonics and Optical Science
Professor

Researcher Profile and Settings

Affiliation

  • Research Institute for Electronic Science Photonics and Optical Science

Job Title

  • Professor

URL

J-Global ID

Research Interests

  • 光制御   光エレクトロニクス   光   光計測   Photophysics   Optical Measurement   Optical Control   Photophysics   

Research Areas

  • Nanotechnology/Materials / Optical engineering and photonics
  • Nanotechnology/Materials / Nanostructure physics
  • Nanotechnology/Materials / Nanostructure chemistry

Association Memberships

  • 応用物理学会   アメリカ光学会   日本光学会   日本化学会   日本分光学会   Optical Society of America   

Research Activities

Published Papers

  • Yoshito Y. Tanaka, Masaya Komatsu, Hideki Fujiwara, Keiji Sasaki
    NANO LETTERS 15 (10) 7086 - 7090 1530-6984 2015/10 [Refereed][Not invited]
     
    We demonstrated a new plasmonic nanodevice that spatially sorts photons according to their colors on the nanoscale while maintaining their nano concentration. The properties of this nanoscale color sorting based on constructive and destructive interferences between different multipolar plasmon modes are controlled by tuning the incidence angle of the incoming photons. The added ability of color sorting and its manipulation could significantly influence the development of possible photonic applications, including nanoscale spectroscopy and sensing.
  • Hideaki Takashima, Kazutaka Kitajima, Yoshito Tanaka, Hideki Fujiwara, Keiji Sasaki
    PHYSICAL REVIEW A 89 (2) 2469-9926 2014/02 [Refereed][Not invited]
     
    Toward complete coupling between propagating light (PL) and a single localized-surface-plasmon (LSP) nanostructure, we propose a tapered-fiber-coupled microspherical cavity system combining an Au-coated probe tip. This system possesses the unique characteristic of precise adjustability for the fiber-cavity coupling rate and the cavity-plasmon coupling rate, which is indispensable for achieving the critical coupling conditions. We successfully demonstrate the 93% PL coupling into the LSP antenna with an effective area of a 58 nm circle, exceeding the diffraction limit.
  • Kyosuke Sakai, Kensuke Nomura, Yoshito Tanaka, Keiji Sasaki
    JOURNAL OF APPLIED PHYSICS 114 (2) 0021-8979 2013/07 [Refereed][Not invited]
     
    We have studied two-dimensional periodically arrayed plasmonic nanogap antennas that exploit a "resonant coupling effect," efficiently collecting incident light and enhancing the nanogap field. A theoretical investigation was carried out on an infinite array of gold nanoblock dimers in a square-lattice arrangement. Under resonant conditions, the near-field intensity spectra in the gap region showed a narrow peak (full width at half maximum of 50 nm) with a field enhancement that was a factor of similar to 5 stronger than that of an isolated single-nanogap antenna. The influence of the geometrical parameters of the array (period, dimer orientation, nanogap size, and number of periods) is discussed. (C) 2013 AIP Publishing LLC.
  • Yoshito Tanaka, Shogo Kaneda, Keiji Sasaki
    Nano Letters 13 (5) 2146 - 2150 1530-6984 2013/05/08 [Refereed][Not invited]
     
    We performed two-dimensional mapping of optical trapping potentials experienced by a 100 nm dielectric particle above a plasmon-resonant gold nanoblock pair with a gap of several nanometers. Our results demonstrate that the potentials have nanoscale spatial structures that reflect the near-field landscape of the nanoblock pair. When an incident polarization parallel to the pair axis is rotated by 90, a single potential well turns into multiple potential wells separated by a distance smaller than the diffraction limit this is associated with super-resolution optical trapping. In addition, we show that the trap stiffness can be enhanced by approximately 3 orders of magnitude compared to that with conventional far-field trapping. © 2013 American Chemical Society.
  • Hideki Fujiwara, Ryo Niyuki, Yoshie Ishikawa, Naoto Koshizaki, Takeshi Tsuji, Keiji Sasaki
    APPLIED PHYSICS LETTERS 102 (6) 0003-6951 2013/02 [Refereed][Not invited]
     
    An unique random laser exhibiting quasi-single-mode and low lasing threshold is developed by a homogenized submicrometer-sized zinc oxide particle film dispersed with intentionally introduced polymer particles as point defects. Such unique random lasing is dominantly initiated at the defect sites, although multi-mode peaks with a collapsed broad emission spectrum are observed at the defect-free sites as in the conventional random lasers. Thus our proposed simple structure can possibly provide the controllability of lasing properties even in random structures. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792349]
  • Naonobu Shimamoto, Yoshito Tanaka, Hideyuki Mitomo, Ryuzo Kawamura, Kuniharu Ijiro, Keiji Sasaki, Yoshihito Osada
    ADVANCED MATERIALS 24 (38) 5243 - 5248 0935-9648 2012/10 [Refereed][Not invited]
  • Yoshito Tanaka, Keiji Sasaki
    APPLIED PHYSICS LETTERS 96 (5) 0003-6951 2010/02 [Refereed][Not invited]
     
    We present a simple method for selecting a single metal nanoparticle with desired localized surface plasmon (LSP) characteristics from particle ensembles on one surface and then transferring it to another surface. The LSP of individual nanoparticles is characterized using a microspectroscopy system. An atomic force microscope mounted on the optical microscope achieves particle capture and release with the chemically modified probe.
  • Daisuke Kawase, Yoko Miyamoto, Mitsuo Takeda, Keiji Sasaki, Shigeki Takeuchi
    JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 26 (4) 797 - 804 0740-3224 2009/04 [Refereed][Not invited]
     
    We calculate the coincidence count probabilities when the photon pairs entangled in orbital angular momentum generated via spontaneous parametric downconversion are measured by using holograms with an in-fold dislocation, considering the nonzero crystal length. We find that the coincidence probabilities related to azimuthal changes in hologram positions deviate significantly from a sinusoidal curve, which has often been assumed in simple analyses. It is found that the main cause of this effect is the high-dimensional entanglement in Laguerre-Gaussian modes. We also find that the crystal length causes the hologram positions to change for the maximum coincidence probabilities. (c) 2009 Optical Society of America
  • Masaru Tanaka, Hirokazu Sato, Yugo Sasaya, Suguru Horinouchi, Jun-ichi Hotta, Yasutaka Matsuo, Kuniharu Ijiro, Keiji Sasaki, Masatsugu Shimomura
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 505 457 - 468 1542-1406 2009 [Refereed][Not invited]
     
    This study describes the preparation of biocompatible patterned surfaces by a two-photon absorption technique. We have synthesized poly(2-methoxyethyl acrylate) copolymers, which exhibit biocompatibility and photocrosslinking moiety. Fabrication resolution can be controlled in the sub-micrometer range by changing the laser power, photoinitiator concentration, and scanning speed. The patterned surfaces showed excellent human platelet compatibility. Biocompatible patterned surfaces can be used in various medical devices, implants, biosensor chips, and tissue engineering scaffolds.
  • Ryo Okamoto, Holger F. Hofmann, Tomohisa Nagata, Jeremy L. O'Brien, Keiji Sasaki, Shigeki Takeuchi
    NEW JOURNAL OF PHYSICS 10 1367-2630 2008/07 [Refereed][Not invited]
     
    Quantum metrology promises greater sensitivity for optical phase measurements than could ever be achieved classically. Here, we present a theory of the phase sensitivity for the general case where the detection probability is given by an N photon interference fringe. We find that the phase sensitivity has a complicated dependence on both the intrinsic efficiency of detection eta and the interference fringe visibility V. Most importantly, the phase that gives maximum phase sensitivity is in general not the same as the phase at which the slope of the interference fringe is a maximum, as has previously been assumed. We determine the parameter range where quantum enhanced sensitivity can be achieved. In order to illustrate these theoretical results, we perform a four-photon experiment with eta = 3/4 and V = 82 +/- 6% (an extension of our previous work (Nagata et al 2007 Science 316 726)) and find a phase sensitivity 1.3 times greater than the standard quantum limit at a phase different to that which gives maximum slope of the interference fringe.
  • Kosei Ueno, Saulius Juodkazis, Vygantas Mizeikis, Keiji Sasaki, Hiroaki Misawa
    ADVANCED MATERIALS 20 (1) 26 - + 0935-9648 2008/01 [Refereed][Not invited]
     
    Gold nanostructures consisting of nanoblocks separated by a few nanometer-wide gaps were fabricated, and found to exhibit strong photoluminescence due to enhancement of the optical near-field localized in the nanogaps. The fabricated structures demonstrate a nanostructured metallic material capable of efficient photoluminescence, whose efficiency can be adjusted by tailoring the nanogap width.
  • Kosei Ueno, Saulius Juodkazis, Vygantas Mizeikis, Dai Ohnishi, Keiji Sasaki, Hiroaki Misawa
    OPTICS EXPRESS 15 (25) 16527 - 16539 1094-4087 2007/12 [Refereed][Not invited]
     
    Periodically corrugated chains of gold nanoblocks, fabricated with high precision by electron-beam lithography and lift-off techniques, were found to exhibit optical signatures of particle plasmon states in which relative contribution of longitudinal multipolar plasmons is significantly lower than that in equivalent rectangular gold nanorods. Plasmonic response of periodic chains is dominated by dipolar plasmon modes, which in the absence of multipolar exciations are seen as background-free and spectrally well-resolved extinction peaks at infrared (IR) wavelengths. This observation may help improve spectral parameters of IR plasmonic sub-wavelength antennae. Comparative studies of plasmon damping and dephasing in corrugated chains of nanoblocks and smooth rectangular nanorods are also presented. (C) 2007 Optical Society of America.
  • Tomohisa Nagata, Ryo Okamoto, Jeremy L. O'Brien, Keiji Sasaki, Shigeki Takeuchi
    SCIENCE 316 (5825) 726 - 729 0036-8075 2007/05 [Refereed][Not invited]
     
    Precision measurements are important across all fields of science. In particular, optical phase measurements can be used to measure distance, position, displacement, acceleration, and optical path length. Quantum entanglement enables higher precision than would otherwise be possible. We demonstrated an optical phase measurement with an entangled four-photon interference visibility greater than the threshold to beat the standard quantum limit-the limit attainable without entanglement. These results open the way for new high-precision measurement applications.
  • Hideki Fujiwara, Yoshio Kawabe, Shigeki Takeuchi, Keiji Sasaki
    PHYSICAL REVIEW A 75 (2) 2469-9926 2007/02 [Refereed][Not invited]
     
    A method to quantitatively evaluate the propagation of parametric fluorescence is proposed. The probability distribution of photon pairs, including the influence of the optical setup in accordance with the wave vector and frequency, is numerically calculated. From this probability distribution, the coincidence counting probability can be simply evaluated. Comparing with experimental data of the iris size dependences of single and coincidence counting rates, the calculated results reproduce the experimental data well without the use of fitting parameters.

Books etc

  • 光科学研究の最前線2
    強光子場科学研究懇談会(JILS) 2009
  • Molecular Nano Dynamics Vol.1
    Wiley-VCH 2009
  • バイオとナノの融合Ⅰ~新生命科学の基礎
    北海道大学出版会 2007
  • 笹木 敬司 
    [北海道大学電子科学研究所] 2004
  • Single Organic Nanoparticles(Edited by H.Masuhara,H.Nakanishi, K.Sasaki)
    Springer 2003
  • Single Organic Nanoparticles(Edited by H.Masuhara,H.Nakanishi,K.Sasaki)
    Springer 2003
  • Single Organic Nanoparticles(Edited by H.Masuhara,H.Nakanishi,K.Sasaki)
    Springer 2003
  • 増原 宏, 中西 八郎, 笹木 敬司 
    Springer 2003 (ISBN: 3540001875)
  • 科学計測のためのデータ処理入門
    CQ出版社 2002
  • 科学計測のためのデータ処理入門
    CQ出版社 2002
  • 新しいフォト二クス時代の材料とデバイス
    TIC出版 2000
  • 新編光学材料ハンドブック
    リアライズ社 2000
  • Organic Mesoscopic Chemistry
    Blackwell Science 1999

Works

  • 文部科学省科学研究費補助金「特定領域研究」(平成16-18年度)略称「極微構造反応」領域番号「432」 分子系の極微構造反応の計測とダイナミクス(Molecular Nano Dynamics) 第6回シンポジウム
    2006
  • 文部科学省科学研究費補助金「特定領域研究」(平成16-18年度)略称「極微構造反応」領域番号「432」 分子系の極微構造反応の計測とダイナミクス(Molecular Nano Dynamics) 第5回シンポジウム
    2006
  • 第1回光-分子強結合反応場シンポジウム
    2006
  • 1st Asian Symposium on Nanotechnology and Nanoscience (Asia NANO 2001)
    2001
  • 10th International Conference on Unconventional Photoactive Systems
    2001
  • International Chemical Congress of Pacific Basin Societies (Pacifichem 2000)
    2000
  • Photon Correlation and Scattering
    2000

Industrial Property Rights

  • 笹木 敬司, 河田 聡, 南 茂夫, 山田 正興  笹木 敬司, 河田 聡  201103020937375721
  • 南 茂夫, 河田 聡, 笹木 敬司  南 茂夫, 河田 聡, 笹木 敬司, 大塚電子株式会社  201103078939405596
  • DNA-金属微粒子系の共振周波数解析方法および共振周波数解析システム
    第3598301号
  • APPARATUS FOR MEASURING POSITION OF FINE PARTICLE
    6867410
  • FINE PARTICLE POSITION MEASURING APPARATUS
    特願 PCT/JP01/01267
  • 微粒子位置計測装置
    第3888829号
  • マイクロボンディング方法
    平10-082311
  • 分光測定装置
    第3311406号
  • 分光測定法
    第3273815号
  • 極微小レーザー光源の形成方法とレーザー発振方法(極微小光源の形成方法)
    第3233957号
  • マルチビーム微粒子操作方法
    第3129471号
  • レーザートラッピング方法
    第2098428号
  • 微粒子動態パターン
    第2544520号
  • 過渡分光波形解析装置
    第2944179号
  • 多入力型過渡波形解析装置
    第2845554号
  • 過渡波形解析装置
    第2911167号
  • 3次元空間分解・時間分解吸収スペクトル測定装置
    第2836859号

Awards & Honors

  • 2007 2007年 Scientific American 50
  • 1999 分子科学研究森野基金奨励賞
  • 1993 国際科学賞芸術のための科学ダビンチ優秀賞
  • 1993 光技術研究振興財団 研究表彰
  • 1992 応用物理学会 光学論文賞
  • 1987 井上研究奨励賞

Research Grants & Projects

  • 量子もつれ合い光子を用いた超解像光計測・加工
    JST戦略的創造研究推進制度(研究チーム型) (戦略的基礎研究推進事業:CREST)
    Date (from‐to) : 2001
  • Super-resolution optical measurement and fabrication techniques using quantum-entangled photons
    JST Basic Research Programs (Core Research for Evolutional Science and Technology :CREST)
    Date (from‐to) : 2001
  • 高機能微小光共振器デバイスの作製と共振器内光ダイナミクスの解析
    科学研究費補助金
    Date (from‐to) : 1999
  • Development of functional optical microcavity devices and analysis of photo-dynamics within the microcavities
    Grant-in-Aid for Scientific Research
    Date (from‐to) : 1999
  • 超高感度フォトンフォース計測技術の開発と分子・細胞系解析への応用
    科学研究費補助金
    Date (from‐to) : 1997
  • Development of high-sensitive photon-force measurement techniques and the applications to analyses of molecular and biological systems
    Grant-in-Aid for Scientific Research
    Date (from‐to) : 1997

Educational Activities

Teaching Experience

  • Inter-Graduate School Classes(General Subject):Natural and Applied Sciences
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : ナノ構造、微細加工、光機能性材料、光化学、液晶、分子性物質、導電性、磁性、薄膜、電子顕微鏡、走査型プローブ顕微鏡、ナノワイヤー、二次元電子ガス、物性理論
  • Photonic Information System
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 情報科学研究科
    キーワード : 光情報処理
  • Photonic Information System
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 情報科学研究科
    キーワード : 光情報処理
  • Optoelectronics
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 光情報処理
  • Photonics
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 光情報処理
  • Exercise in Electronic Information Engineering Ⅱ
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 回路の過渡応答,伝送線路の基本特性.pn接合、ショットキー接合、MOS構造、バイポーラトランジスタ、MOSFET,発光遷移と光吸収,光共振器
  • Exercise in Electrical and Electronic Engineering IV
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 回路の過渡応答,伝送線路の基本特性.pn接合、ショットキー接合、MOS構造、バイポーラトランジスタ、MOSFET,発光遷移と光吸収,光共振器

Campus Position History

  • 2013年5月27日 
    2015年3月31日 
    研究戦略室室員
  • 2014年4月1日 
    2015年9月30日 
    電子科学研究所附属グリーンナノテクノロジー研究センター長
  • 2015年4月1日 
    2017年3月31日 
    研究戦略室室員

Position History

  • 2013年5月27日 
    2015年3月31日 
    研究戦略室室員
  • 2014年4月1日 
    2015年9月30日 
    電子科学研究所附属グリーンナノテクノロジー研究センター長
  • 2015年4月1日 
    2017年3月31日 
    研究戦略室室員


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