Contribution of non-linear polarization in non-linear optical process

• Project/Area Number: 18K03485
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: The University of Tokyo
• Principal Investigator: Iwasaki Atsushi 東京大学, 大学院理学系研究科(理学部), 教授 (30447073)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000); Fiscal Year 2020: ¥130,000 (Direct Cost: ¥100,000、Indirect Cost: ¥30,000); Fiscal Year 2019: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
• Keywords: フェムト秒レーザー / アブレーション / 過渡反射 / 二温度モデル / 過渡反射率測定 / joint-density-of-states / 極端紫外 / 数サイクル / 誘電率 / 反射率 / 時間分解分光法 / 極端紫外パルス / ブースター増幅器 / 非線形光学過程 / 非線形分極率 / 超高速ダイナミクス

Outline of Final Research Achievements

It is well known that on metal surface, the reflectance changes with time due to absorption and excitation by light pulses, which means that the excitation of electronic temperature by electronic excitation right after the absorption of photons is relaxed to the surrounding lattice system. In this study, it was clarified by comparison between experiments and simulations that the temporal change of reflectance caused by ultraviolet light pulse excitation on the solid surface is due to the transient change of permittivity. It was found that increasing the excited fluence induces a change in the permittivity by increasing the excited state.

Academic Significance and Societal Importance of the Research Achievements

様々な物質と光との相互作用を応用した光を使った技術は、身の回り環境の計測やものづくりに用いられています。この研究では、光が物質と相互作用するときに、最初に起きる主な過程である光吸収と、物質がその結果どのように励起されて結合解離やアブレーションなどの物質加工に至るのか、ということについて、短い時間での物質の様子を実時間に観測する手法を用いて測定しました。この結果を再現するかシミュレーションしたところ、試料膜厚や光励起フルエンス、励起波長による実験条件の違いによる実験結果をよく再現することが明らかとなりました。

Research Products

• [Journal Article] サブフェムト秒分解能で観る光の場の中の分子および固体の超高速ダイナミクス (2019)
  • Author(s): 岩崎純史, 山内 薫
  • Journal Title: 光アライアンス Volume: 30 Pages: 28-33
  • NAID: 40021765898
• [Presentation] Ultrafast electron relaxation and phonon thermalization process in gold thin film observed by transient reflectometry (2021)
  • Author(s): Ryosuke Hayashi, Atsushi Iwasaki Parinda Vasa, Kaoru Yamanouchi
  • Organizer: Symposium on Recent Development in Ultrafast Intense Laser Science 2
  • Int'l Joint Research / Invited
• [Presentation] Ultrafast electron relaxation and phonon thermalization processes in gold thin film observed by transient reflectometry (2020)
  • Author(s): Ryosuke Hayashi, Atsushi Iwasaki Parinda Vasa, Kaoru Yamanouchi
  • Organizer: 第１４回分子科学討論会2020 オンライン討論会
• [Presentation] Next generation soft X-ray light sources and applications (2020)
  • Author(s): Atsushi Iwasaki
  • Organizer: Symposium on Recent Development in Ultrafast Intense Laser Science
  • Int'l Joint Research
• [Presentation] Ultrafast electron relaxation process after optical excitation of gold thin film at 400 nm by transient reflectometry (2019)
  • Author(s): Astushi Iwasaki, Ryosuke Hayashi, Kaoru Yamanouchi
  • Organizer: 第13回分子科学討論会
• [Presentation] シードFELによるコヒーレント極端紫外パルス光源 (2019)
  • Author(s): 岩崎 純史
  • Organizer: PF研究会「高繰り返し極短パルス光源の未来」
  • Invited