Efficient nearly-circularly-polarized terahertz generation from an air plasma pumped by collinear and circularly polarized two-color laser fields
Qiying Song, Qinggang Lin, Honggeng Wang, Haizhe Zhong, Yi Cai, Shuiqin Zheng, Zhenkuan Chen, Xiaowei Lu, Xuanke Zeng, Huangcheng Shangguan, Hongyu Wang, Shixiang Xu
Abstract
Efficient circularly polarized terahertz (THz) emission is important for THz imaging technology and basic scientific research. In order to achieve this, we have made a simple, all-passive design to achieve collinear and corotating circularly polarized two-color laser fields. The collinearity allows us to manipulate accurately the relative phase between two-color lasers. For a given relative phase, our experiments show that efficient nearly-circularly-polarized THz emission can be generated from an air plasma pumped by the two-color fields. The emitted THz power is \ensuremath{\sim}2.5 times that pumped by linear-polarized two-color laser fields. Our results also indicate that nearly circularly polarization is stable against different pump power and plasma distance.