Hasegawa, Taro

写真a

Affiliation

Faculty of Science and Technology, Department of Physics (Yagami)

Position

Assistant Professor/Senior Assistant Professor

E-mail Address

E-mail address

Related Websites

External Links

Career 【 Display / hide

  • 1996.04
    -
    2000.09

    Research Associate, Dept. Electronics and Computer Science, Science Univ. of Tokyo in Yamaguchi

  • 2000.09
    -
    2005.03

    Research Associate, Dept. of Material Science, Faculty of Science, Himeji Institute of Technology (The institute was united and renamed as "Univ. of Hyogo" from Apr. 2004.)

  • 2003.01
    -
    2004.03

    Guest Researcher, Time and Frequency division, National Institute of Standards and Technology (NIST), United States of America

  • 2005.04
    -
    Present

    Assistant Professor, Dept. Physics, Fac. Sci.&Tech., Keio Univ.

  • 2010.07
    -
    2010.09

    Guest Researcher (Max-Planck-Institut fuer Quantenoptik)

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Research Areas 【 Display / hide

  • Atomic/Molecular/Quantum electronics (Atomic/Molecular/Quantum Electronics, Plasma)

Research Keywords 【 Display / hide

  • Ion traps

  • Laser cooling

  • Optical Frequency Comb Generators

  • Nonlinear Optics

  • High-resolution spectroscopy

Research Themes 【 Display / hide

  • 大きな蛍光観測立体角をもつイオントラップの開発, 

    2015.04
    -
    Present

  • 光周波数コムを用いた高分解能分光, 

    2013.04
    -
    Present

  • New ion-trapping scheme for quantum computing, 

    2004
    -
    2005

     View Summary

    Implementation of quantum computers using the quantum states of ions
    in a new ion trap.

 

Books 【 Display / hide

  • ペンギン物理学辞典

    清水忠雄ほか合計21名, 朝倉書店, 2012

  • 光学実験の基礎と改良のヒント

    UEHARA KIYOJI, HASEGAWA TARO, SASADA HIROYUKI, 講談社サイエンティフィク, 2009

    Scope: 63-112

Papers 【 Display / hide

  • 260 kHz mode-spacing optical frequency combs for scan-free high-resolution direct-comb spectroscopy

    Taro Hasegawa

    Optics Express (The Optical Society)  28 ( 22 ) 32837 - 32846 2020.10

    Research paper (scientific journal), Single Work, Accepted

     View Summary

    For scan-free high-resolution direct-comb spectroscopy, mode spacing of an optical
    frequency comb is reduced down to 260 kHz by phase modulation. It turns out that timedomain signal is degraded by averaging because of slow optical path length fluctuations and
    fast optical pulse timing jitter. In this study, compensation of these effects is introduced, and
    signal degradation by averaging is avoided. With demonstrations of direct-comb spectroscopy
    with the narrow-mode-spacing optical frequency comb, Doppler-limited absorption spectrum of
    methane and reflection spectrum from an optical ring cavity are observed. As a result, detailed
    resonance spectral line profile of 8 MHz linewidth for the optical ring cavity is obtained in 50 ms
    measurement time.

  • Robust offset locking of laser frequency with electronically tunable LC circuits for sub-millihertz uncertainty

    Yuhei Seishu, Taro Hasegawa

    Applied Physics B (Springer)  125 ( 8 ) 142(1) - 142(8) 2019.07

    Research paper (scientific journal), Joint Work, Accepted

  • Mode Density Multiplication of an Optical Frequency Comb by N^{2} with Phase Modulation

    Hasegawa T., Sasada H.

    2018 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2018 (2018 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2018)   2019.04

    ISSN  9781943580453

     View Summary

    © 2018 OSA. We introduce a simple scheme for mode density multiplication of an optical frequency comb by square of an arbitrary integer with phase modulation. The mode density of an Er fibercomb is multiplied by 4 2 .

  • Mode density multiplication of an optical frequency comb by N<sup>2</sup> with phase modulation

    Hasegawa T.

    Optics Express (Optics Express)  26 ( 19 ) 24551 - 24563 2018.09

     View Summary

    © 2018 Optical Society of America. We introduce a simple scheme for mode-density multiplication of an optical frequency comb (OFC) by a factor of square of an arbitrary integer N using phase modulation. This scheme is employed to multiply the mode density of an erbium-doped fiber laser OFC (repetition rate of 66.87 MHz) by factors of 42, 82, and 3 · 42 using an electro-optic phase modulator. The OFC multiplied by 42 is applied to direct-comb spectroscopy of methane with a spectral resolution of 4.18 MHz.

  • A radio-frequency ion trap with string electrodes

    KANAI DAISUKE, HASEGAWA TARO

    Review of Scientific Instruments (American Institute of Physics)  89 ( 2 ) 023106 2018.02

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00346748

     View Summary

    © 2018 Author(s). A radio-frequency (rf) ion trap with string electrodes is introduced. In this trap configuration, the rf electrodes are made of narrow metal strings, by which a negligibly small portion of light-induced fluorescence (LIF) is blocked. Then the LIF collection solid angle can be maximized. In the demonstration, barium ions are trapped and laser-cooled in the rf trap with string electrodes successfully, and the crystallization is confirmed by the LIF spectrum.

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Papers, etc., Registered in KOARA 【 Display / hide

Reviews, Commentaries, etc. 【 Display / hide

  • 強度画像にはない位相画像の表現力 (翻訳)

    HASEGAWA TARO

    パリティ (丸善)     14 - 21 2018.02

    Introduction and explanation (commerce magazine)

Presentations 【 Display / hide

  • 高分解能コム直接分光のスペクトル取得時間の高速化

    大平一徹, 長谷川太郎

    日本物理学会第76回年次大会 (オンライン) , 2021.03, Oral Presentation(general), 日本物理学会

  • 高分解能コム直接分光のためのモード間隔 260 kHz の光周波数コム

    長谷川太郎

    2020年度日本分光学会年次講演会 (オンライン) , 2020.10, Oral Presentation(general), 日本分光学会

  • 位相変調による光周波数コム直接分光の1 MHz以下の高分解能化

    長谷川太郎

    日本物理学会 2020年秋季大会 (オンライン) , 2020.09, Oral Presentation(general), 日本物理学会

  • パワー損失のない光周波数コムの繰り返し周波数高速化

    蔭山大起、長谷川太郎

    日本物理学会第75回年次大会 (名古屋大学) , 2020.03, Oral Presentation(general), 日本物理学会

  • Robust offset locking of laser frequency with electronically tunable LC circuits for sub-millihertz uncertainty

    Taro Hasegawa, Yuhei Seishu

    2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (International Congress Centre Munich, Germany) , 2019.06, Poster (general)

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • 光周波数コムを用いた超高分解能高速高精度分光法の開発

    2019.04
    -
    2020.03

    公益財団法人精密測定技術う振興財団, 精密測定技術振興のための調査・研究事業, 長谷川太郎, Research grant, Principal Investigator

  • 変位型サニャック干渉計を用いた超短パルスレーザーのパルス時間測定器

    2019.04
    -
    2020.03

    慶應義塾大学, 学事振興資金, 長谷川太郎, Research grant, Principal Investigator

  • インコヒーレント光源の1光子吸収によるイオントラップへのイオンローディング法

    2018.04
    -
    2019.03

    慶應義塾大学, 学事振興資金, 長谷川太郎, Research grant, Principal Investigator

  • 回転rfトラップにおけるダストプラズマの挙動

    2016.04
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    2017.03

    慶應義塾大学, 学事振興資金, 長谷川太郎, Research grant, Principal Investigator

  • 新しい広帯域かつ狭線幅な赤外分光法

    2015.04
    -
    Present

    日本学術振興会, Grant-in-Aid for Scientific Research, 長谷川太郎, Research grant, Principal Investigator

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Courses Taught 【 Display / hide

  • PHYSICS LABORATORIES 2

    2021

  • PHYSICS LABORATORIES 1

    2021

  • OPTICS

    2021

  • LITERATURE OF PHYSICS

    2021

  • LASER PHYSICS

    2021

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Courses Previously Taught 【 Display / hide

  • Optics

    Keio University, 2017, Spring Semester, Major subject, Within own faculty

  • Laser Physics

    Keio University, 2017, Spring Semester, Within own faculty

  • Optics

    Keio University, 2016, Spring Semester, Major subject, Within own faculty

  • Optics

    Keio University, 2015, Spring Semester, Major subject, Within own faculty

  • Laser Physics

    Keio University, 2015, Spring Semester, Within own faculty

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Memberships in Academic Societies 【 Display / hide

  • Physical Society of Japan

     
  • American Physical Society

     
  • Optical Society of America

     
  • The Spectroscopical Society of Japan

     

Committee Experiences 【 Display / hide

  • 2012.04
    -
    2014.03

    Editor, Physical Society of Japan

     View Remarks

    日本物理学会誌

  • 2007.11
    -
    2008.10

    Program committee of Quantum Electronics subsection, section 1, Physical Society of Japan