KEIO RESEARCHERS INFORMATION SYSTEM

Other Affiliation 【 Display / hide 】

Other Affiliation 【 Display / hide 】

• 東京大学教養学部, 非常勤講師

Career 【 Display / hide 】

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 】

Research Areas 【 Display / hide 】

• Natural Science / Semiconductors, optical properties of condensed matter and atomic physics (Atomic/Molecular/Quantum Electronics, Plasma)

Research Keywords 【 Display / hide 】

Research Keywords 【 Display / hide 】

• Ion traps

• Laser cooling

• Optical Frequency Comb Generators

• Nonlinear Optics

• High-resolution spectroscopy

Research Themes 【 Display / hide 】

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 】

Books 【 Display / hide 】

• 新物理学ライブラリ1　物理学　新訂第2版

  阿部龍蔵, 川村清,　佐々田博之, 長谷川太郎, 蘆田祐人, サイエンス社, 2024.08

• 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 】

Papers 【 Display / hide 】

• Evaluation of the Sagnac-loop laser frequency stabilization to sub-Doppler spectral lines: erratum

  Taro Hasegawa

  Journal of Optical Society of America B (Optica)  42 ( 1 ) 18 - 18 2024.12

  Research paper (scientific journal), Single Work, Lead author, Last author, Corresponding author, Accepted

  • Access to Document (DOI)

• Phase structure of harmonically mode-locked optical frequency combs

  Taro Hasegawa

  Optics Express (Optica)  32 ( 5 ) 8092 - 8100 2024.02

  Research paper (scientific journal), Single Work, Lead author, Last author, Corresponding author, Accepted

  　View Summary

  Carrier phase of a harmonically mode-locked optical frequency comb (OFC) is investigated in detail. While harmonically mode-locked OFCs show promise for high-repetition-rate applications, their mode spacing is not the same as the pulse repetition rate, unlike fundamentally mode-locked OFCs. Consequently, harmonically mode-locked OFCs are unsuitable for applications requiring OFCs with wide mode spacing. This study examines the pulse-to-pulse carrier phase evolution of 4th- and 5th-order harmonically mode-locked OFCs, revealing uneven carrier phase evolution responsible for the narrow mode spacing. The possibility of achieving harmonically mode-locked OFCs with wide mode spacing is suggested by implementing pulse-to-pulse phase modulation to ensure even phase evolution.

  • Access to Document (DOI)

• Evaluation of the Sagnac-loop laser frequency stabilization to sub-Doppler spectral lines

  Taro Hasegawa

  Journal of Optical Society of America B (Optica)  40 ( 3 ) 667 - 672 2023.03

  Single Work, Lead author, Last author, Corresponding author, Accepted,  ISSN  07403224

  　View Summary

  Laser frequency stability locked to D2 transition of 85Rb at 780 nm by the Sagnac-loop stabilization scheme was evaluated using the heterodyne measurement with an optical frequency comb. This scheme does not require modulation and magnetic field to generate the feedback error signal. Therefore, the setup for the laser frequency stabilization is simple. Because of the mechanical stability of the Sagnac interferometer, the dispersion of atom transition, which is used as an error signal for feedback loop, can be observed with negligibly small effects of mechanical fluctuations. In the experiment, the Allan variance for relative frequency uncertainty was 2.6×10-12 over 64 s averaging.

  • Access to Document (DOI)

• Mode spacing of harmonic mode-locked optical frequency combs

  Hasegawa T.

  Hyperspectral/Multispectral Imaging and Sounding of the Environment in Proceedings Optica Sensing Congress 2023, AIS, FTS, HISE, Sensors, ES - Part of Optical Sensors and Sensing Congress 2023  2023

  　View Summary

  Mode spacing of an optical frequency comb of a harmonic mode-locked laser is studied by using an optical cavity. It turns out that mode spacing disagrees with pulse repetition rate for the harmonic mode-locked comb.

  • Access to Document (DOI)

• Mode spacing of harmonic mode-locked optical frequency combs

  Hasegawa T.

  Applied Industrial Spectroscopy in Proceedings Optica Sensing Congress 2023, AIS, FTS, HISE, Sensors, ES 2023  2023

  　View Summary

  Mode spacing of an optical frequency comb of a harmonic mode-locked laser is studied by using an optical cavity. It turns out that mode spacing disagrees with pulse repetition rate for the harmonic mode-locked comb.

  • Access to Document (DOI)

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

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

• Ion traps for simulation of frustrated quantum states

  Hasegawa, Taro

  学事振興資金研究成果実績報告書 (慶應義塾大学)  2022

• Novel optical frequency combs for exoplanet search

  Hasegawa, Taro

  学事振興資金研究成果実績報告書 (慶應義塾大学)  2021

• Pulse width measurement of ultrashort pulse lasers with a displaced Sagnac interferometer

  Hasegawa, Taro

  学事振興資金研究成果実績報告書 (慶應義塾大学)  2019

• Ion loading into ion traps by one-photon absorption from an incoherent light source

  Hasegawa, Taro

  学事振興資金研究成果実績報告書 (慶應義塾大学)  2018

• Novel infrared broadband and high-resolution spectroscopy

  Hasegawa, Tarō

  科学研究費補助金研究成果報告書 2017

Reviews, Commentaries, etc. 【 Display / hide 】

Reviews, Commentaries, etc. 【 Display / hide 】

• 長波長の赤外域での光周波数コム直接分光

  長谷川　太郎

  分光研究 (日本分光学会)  71 ( 3 ) 72 - 74 2022.06

  Article, review, commentary, editorial, etc. (scientific journal), Single Work, Lead author, Last author, Corresponding author

• 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

  Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)

Presentations 【 Display / hide 】

Presentations 【 Display / hide 】

• 高調波モード同期光周波数コムの位相構造

  長谷川太郎

  日本物理学会第79回年次大会 (北海道大学) , 

  2024.09

  , 

  Oral presentation (general), 日本物理学会

• サニャック分光による周波数安定化レーザーの評価

  長谷川太郎

  日本物理学会2023年春季大会 (オンライン) , 

  2024.03

  , 

  Oral presentation (general), 日本物理学会

• 高調波モード同期光周波数コムのモード間隔

  長谷川太郎

  日本物理学会第78回年次大会 (東北大学) , 

  2023.09

  , 

  Oral presentation (general), 日本物理学会

• Mode spacing of harmonic mode-locked optical frequency combs

  Taro Hasegawa

  Optica Sensing Congress (Munich) , 

  2023.07

  -

  2023.08

  , 

  Poster presentation

• サニャック分光レーザー周波数安定化の長期安定度改善

  長谷川太郎

  日本物理学会2024年春季大会 (オンライン) , 

  2023.03

  , 

  Oral presentation (general), 日本物理学会

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

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

• ストリング rf イオントラップでの量子情報

  2024.10

  -

  2028.03

  国立研究開発法人 科学技術振興機構, さきがけ「量子・古典の異分野融合による共創型フロンティアの開拓」, Commissioned ｒesearch, Principal investigator

• 高分解能と広帯域を併せ持つコム直接分光の開発

  2021.04

  -

  2024.03

  日本学術振興会, Grant-in-Aid for Scientific Research, 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, Research grant, Principal investigator

• 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, 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, Research grant, Principal investigator

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Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• PHYSICS SEMINAR 2

  2024

• PHYSICS LABORATORIES 2

  2024

• PHYSICS LABORATORIES 1

  2024

• OPTICS

  2024

• LITERATURE OF PHYSICS

  2024

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Courses Previously Taught 【 Display / hide 】

Courses Previously Taught 【 Display / hide 】

• Optics

  Keio University

  2017.04

  -

  2018.03

  , 

  Spring Semester, Within own ｆaculty

• Laser Physics

  Keio University

  2017.04

  -

  2018.03

  , 

  Spring Semester, Within own ｆaculty

• Optics

  Keio University

  2016.04

  -

  2017.03

  , 

  Spring Semester, Within own ｆaculty

• Optics

  Keio University

  2015.04

  -

  2016.03

  , 

  Spring Semester, Within own ｆaculty

• Laser Physics

  Keio University

  2015.04

  -

  2016.03

  , 

  Spring Semester, Within own ｆaculty

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Memberships in Academic Societies 【 Display / hide 】

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 】

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