2022 Fiscal Year Final Research Report
Study on mechanism of THz wave radiation from laser plasma of liquid films
| Project/Area Number |
20K05371
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 30020:Optical engineering and photon science-related
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| Research Institution | Setsunan University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | テラヘルツ波 / 衝撃波 / レーザープラズマ / 水 / 気体 |
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| Outline of Final Research Achievements |
To investigate the mechanism of terahertz wave emission from a double-pulse excited water film target, time-resolved shadowgraph and time-integrated emission images were obtained. The results indicate that interactions between the shockwave-front and the laser pulse are responsible for the enhancement of terahertz emission.
The interaction between shockwaves and laser pulses were investigated in detail by terahertz emission measurements from a double-pulse-excited air target. The offset position dependence of the terahertz polarization state indicates that the terahertz electric field is perpendicular to the shock wavefront.
Based on these observations, we propose a model in which tansient current induced by the steep electron density gradient at the shockwave front excited by fs optical pulses generates the terahertz emssion.
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| Free Research Field |
テラヘルツ波工学
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| Academic Significance and Societal Importance of the Research Achievements |
衝撃波波面からのテラヘルツ放射現象を（代表者の知る限り）初めて観測した．これは誘起された急峻な電子密度勾配を持つレーザープラズマ中に生じる過渡電流による放射であることを示した．今後，バイアス電圧印加や2色光パルス励起を適用することでさらなる放射テラヘルツ波強度の増強や新規現象の発現が期待できる．
本研究のテラヘルツ波放射実験は，レーザパルス照射により発生した衝撃波の密度構造及びその高速時間変化を調査する手段として利用できる．複数のプリパルスを用いることで衝撃波どうしの相互作用についてシャドウグラフ観察をはじめとする従来の分析法では得難い知見が得られる可能性がある．
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