Terahertz wave generation from laser-induced air plasma influenced by the external electric field

Terahertz wave generation from laser induced air plasma has a close relevance with the applied external electric field. In this paper, by applying a high-voltage DC electric filed onto the laser induced air plasma, we demonstrated that the amplitude of generated terahertz wave increases linearly with the external electric field strength, the terahertz amplitude and power are quadratic in the lower power region and the terahertz amplitude is linear with the pump light power in the high power region. Moreover, the polarization direction of the generated terahertz wave changes synchronously with the direction of applied external electric field. The results proved the effect of external electric field on the power and polarization of terahertz wave generation from laser induced air plasma.