Abstract-Sequential terahertz pulse generation by photoionization and coherent transition radiation in underdense relativistic plasmasp

J.Déchard, A. Debayle, X. Davoine, L. Gremillet, L. Bergé

(Submitted on 14 Sep 2017)

https://arxiv.org/abs/1709.04639

Terahertz (THz) emission by two-color, ultrashort optical pulses interacting with underdense helium gases at ultrahigh intensities (>1019W/cm2) is investigated by means of 3D particle-in-cell simulations. The THz field is shown to be produced by two mechanisms occurring sequentially, namely, photoionization-induced radiation (PIR) by the two-color pulse and coherent transition radiation (CTR) by the wakefield-accelerated electrons escaping the plasma. For plasmas of atomic densities >1017cm−3, CTR proves to be the dominant process, providing THz bursts with field strength as high as 100GV/m and energy in excess of 1mJ. Analytical models are developed for both the PIR and CTR processes, which correctly reproduce the simulation data.