High-Field Coherent Terahertz Radiation Generation From Chirped Laser Pulse Interaction With Plasmas

Abstract

This article presents a theoretical analysis of high-field terahertz (THz) radiation generation from chirped laser pulse interaction with a plasma of slanting density modulation. The mechanism is based on strong nonlinear transverse current produced by the beating of two chirped laser pulses, where the plasma density modulation is inclined at angle to the propagation of the lasers. We claim that oblique spatial density ripple plays a crucial role in field enhancement of THz. At resonance (due to the phase-matching), the field strength of THz becomes maximum for a particular slating angle of the plasma density modulation. We claim that the oblique spatial density ripple and laser frequency-chirp combinedly play a crucial role in field enhancement of THz field. We observe that stable THz is generated with a maximum field strength of 100 MV/cm and a relatively broad spectrum extending out to 2.4 THz, with a strong dependence on the selection of slating angle of plasma density ripple and laser frequency chirp parameter, which corresponds to the conversion efficiency in order of 10−2. The efficiency of the process may be optimized and controlled by the laser and plasma parameters, which may be useful in various applications of these kind of high-field THz.