Numerical simulations of THz emission from the laser wakefields through linear mode conversion

Abstract

A nonlinear one-dimensional particle-in-cell (PIC) program is used to simulate the generation of high power terahertz (THz) emission from the interaction of an ultrashort intense laser pulse with underdense plasma under magnetized and unmagnetized cases. The magnetic field in laser-irradiated plasma has an important effect on the resonant absorption, and makes the results different. The spectra of THz radiation are compared under different cases (with or without external magnetic field), and the optimized parameters including plasma density scale length, incident angle and external magnetic field are calculated. High-amplitude electron plasma wave driven by a laser wakefield can produce powerful THz emission through linear mode conversion under certain conditions. With incident laser intensity of 1018W/cm2, the generated emission is computed to be of the order of several MV/cm field and tens of MW level power. It is suitable for the studies of high-field and nonlinear physics in the THz regime.