Terahertz Wave Modulation by Pre-plasma Using Different Laser Wavelength
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We report the terahertz (THz) wave modulation from a pre-plasma using different laser wavelengths, which is intersected orthogonally to the two-color laser filament produced by 800-nm laser pulse. When the pre-plasma exists, the THz radiation excited by the two-color field decreases significantly and the modulation depth increases with the increasing modulation pulse wavelength. Moreover, the amplitude reduction at high frequency in THz spectrum and the THz wave polarization change also have the modulation pulse wavelength dependence. These results can be explained by a photocurrent model considering wavelength-dependent ionization rate. The work contributes to further understand the theoretical mechanism of THz wave generation and enrich the practical application of ultrafast THz modulator.
KeywordsTerahertz Plasma Photoionization Modulation
The authors acknowledge support from the National Natural Science Foundation of China under grant no. 61905271.
This work was funded by the Beijing Advanced Innovation Center for Imaging Technology and Beijing Natural Science Foundation under Grant No. JQ18015.