Excitation of terahertz radiation by parametric mixing of four waves in magnetized plasma

Abstract

THz radiation may be excited by nonlinear mixing of two counter-propagating laser beams, having frequency difference ω1∼ω2≥2ωp, in under dense plasma. Beating laser beams exert nonlinear ponderomotive force on plasma electrons and excite a nonlinear density perturbation. The nonlinear density perturbation drives a non-resonant space charge mode which may excite a pair of plasma wave and back scattered electromagnetic terahertz wave at resonance. The presence of transverse magnetic field further enhances the growth of THz wave. The transverse magnetic field also tunes the amplitude and frequency of THz wave. The maximum growth rate of excitation process Γ∼6.22×10−6 s−1 is achieved for applied magnetic field ∼175 kG.