Polarization control of terahertz waves generated by a femtosecond three-color pulse scheme

Abstract

Polarization characteristics of terahertz waves generated from a short air plasma excited by femtosecond three-color pulses with a frequency ratio of 1:2:3 have been theoretically investigated, and the results show that flexible and effective control of terahertz polarization can be achieved by means of changing the polarization combination and relative phase of three-color pulses, which is related to the electric field spatiotemporal distribution of the synthetic pulse formed via three-color pulse superposition. The complicated spatiotemporal distribution can be made clear by analyzing the projection component of the electric field in the three-dimensional Cartesian coordinate system. For terahertz waves generated from a short air plasma filament, the proposed method of terahertz polarization control on the basis of a three-color pulse scheme can be realized by ordinary multi-cycle laser pulses and overcome the disadvantage of few-cycle laser pulses utilized to obtain nearly circularly polarized intense terahertz waves or elliptically polarized intense terahertz waves with large ellipticity in the two-color pulse scheme.