研究目的
Investigating the efficient generation of THz pulses by high power near IR laser radiation in a low-pressure gas cell to avoid multiple filamentation and excessive ionization.
研究成果
The optimization of gas pressure, pulse duration, and the second harmonic crystal position allowed obtaining a THz pulse of about 1.5 μJ energy. Maximal conversion efficiency into THz range is observed in the single filament regime of laser pulse propagation.
研究不足
Saturation of THz yield due to plasma limitation of laser intensity is a challenge for TW pulses. The need to exclude gas cell windows and decrease pressure below 10 mbar to avoid saturation.
1：Experimental Design and Method Selection:
The study used a two-color scheme with 2 TW, 30 fs, 800-nm laser pulses and their second harmonic focused in a low-pressure gas cell.
2：Sample Selection and Data Sources:
Nitrogen, atmospheric air, and argon were used as the sample gases.
3：List of Experimental Equipment and Materials:
'Pulsar 200 TW' laser system, KDP crystal for second harmonic generation, Golay cell for THz energy measurement, and various THz filters.
4：Experimental Procedures and Operational Workflow:
Laser pulses were focused in a long vacuum cell, and THz energy was measured with a Golay cell equipped with THz filters.
5：Data Analysis Methods:
THz spectral shape was estimated using transmission spectra of filters and electro-optical sampling method.
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