Modulation of terahertz wave generation from laser-induced filament based on a preionized plasma

Abstract We demonstrate the modulation of terahertz wave generation from two-color femtosecond laser filament on the basis of a preionized air plasma background created by a modulation pulse using an orthogonal pumping geometry. This is achieved by adjusting and optimizing the phase difference between the two-color laser fields, which is introduced when the two-color fields goes through the preionized air plasma. In experiments, terahertz time domain waveform is observed using electro-optics sampling setup. Both the energy and the waveform of terahertz wave change significantly with the increase of modulation pulse energy. The results are reasonably coincident with our theoretical simulation based on the plasma photocurrent model. We also experimentally observe the additional relative phase between the two-color laser fields due to the presence of the preionized air plasma. Our results can contribute to the further understanding of the generation mechanism of terahertz wave, enhance the generation efficiency and expand the practical application of terahertz wave.