研究目的
Investigating the effect of an azimuthal phase modulation of the second harmonic (SH) carrying an optical vortex charge on the intensity and phase distribution of the THz pulse emitted from the laser induced plasma filament in air.
研究成果
The experimental results are in good agreement with the theoretical predictions when using vortex driver beams. The investigations open new routes towards an active control of ultra-broadband THz beam properties.
研究不足
The study is limited to the analysis of THz radiation generated in air by femtosecond optical vortex pulses. The modulation depth of THz intensity is frequency dependent, which may limit the applicability across all THz frequencies.
1：Experimental Design and Method Selection:
The study uses a plasma photocurrent model to theoretically analyze the effect of SH vortex charge on THz radiation. Experimentally, it investigates THz wave generation from plasma filaments formed by focused bichromatic femtosecond laser pulses.
2：Sample Selection and Data Sources:
The experiment uses air as the medium for plasma filament formation.
3：List of Experimental Equipment and Materials:
A 1 kHz repetition rate femtosecond Ti:sapphire chirped pulse amplification laser system (Legend elite duo HE+, Coherent Inc.), delivering 40 fs (FWHM) light pulses centred at 800 nm with maximal pulse energy of 8 mJ. A thermal camera for THz wave imaging.
4：Experimental Procedures and Operational Workflow:
The FH was kept as a Gaussian beam, and the SH was modulated with an optical vortex charge. THz radiation was imaged with a thermal camera.
5：Data Analysis Methods:
The intensity and phase distribution of the THz pulse were analyzed both theoretically and experimentally.
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