Generation of THz radiation by parametric coupling of laser and Trivelpiece–Gould mode

Abstract

A scheme to generate terahertz radiation is proposed, wherein the high power, perpendicular-extraordinary laser pump (X-mode) (ω0) parametrically decays into the Trivelpiece-Gould (TG) (ω1) mode and kinetic Alfvén wave (ω2) at an oblique angle with the external magnetic field. The nonlinear interaction amongst the three interacting waves leads to the existence of quasi-static ponderomotive force. Furthermore, under the influence of this force, electrons acquire nonlinear oscillatory velocity. A strong transient current is generated by the nonlinear coupling of laser velocity and TG density perturbation. This nonlinear current drives a wave, whose frequency is obtained in the terahertz range (ω2=ω0−ω1) after optimizing various laser-plasma parameters. For the resonant excitation of the wave, the requisite phase matching condition is shown by modelling the parallelogram, which follows the principle of conservation of energy and momentum simultaneously. The coupling coefficients for the three-wave interaction process along with the growth rate of decay instability are investigated.