The study of terahertz wave generation via pre-ionized air plasma

Abstract

The methods of terahertz (THz) wave generation has attracted considerable attention in recent years because it involves a complex plasma process. The theories used to explain the intrinsic mechanism of laser ionization of air to produce THz wave are not particularly numerous, further exploration of its mechanism in the air is necessary. We report the THz wave generation from single color scheme modulated by pre-ionized air plasma via an orthogonal pumping geometry. It is found that the amplitude of the THz signal generated by the pump beam tends to decrease gradually with the increase of the modulation power. We believe that the ponderomotive force plays an important role in the process of the interaction between the pump beam and pre-ionization beam. The hydrostatic state of the electrostatic separation field caused by modulation beam will directly affect the generation efficiency of the THz wave. Our results contribute to further understanding of the theoretical mechanism and expanding of the practical applications of THz wave generation and modulation.