Bright terahertz (THz) generation by frequency mixing of dichromatic lasers in inhomogeneous cold plasma: Scaling of THz field

Abstract

We report a theoretical model for bright, radially polarized terahertz (THz) generation based on difference frequency generation in periodic density plasmas. An initial phase difference between two lasers is incorporated in our model. It is observed that the THz field significantly varies with the initial phase difference. It is also found that the THz field and efficiency depend on the periodic plasma density structure parameters (like amplitude nγ and wave vector γ). Our investigations reveal that close to the phase matching condition, and optimized values of laser and plasma parameters, peak THz fields ∼ 15 GV/m can be obtained for the laser field ∼ 5×1010 V/m. We also found that the THz field distribution can be controlled with laser field profile parameters. The conversion efficiency of ∼0.01 can be achieved by optimizing the laser field profile and plasma parameters. In our model, high field and radially polarized THz can be obtained to meet the demands of THz-matter interactions, nonlinear THz spectroscopy, imaging, etc. Radially polarized THz field is also useful to penetrate deeply into the layers inside the skin with less risk of collateral damage and thereby improved safety and efficacy of treatment.