THz generation by cross-focusing of two laser beams in a rippled density plasma

Abstract

A scheme of terahertz (THz) generation by the cross-focusing of two collinear Gaussian lasers is investigated with frequency difference in spatially periodic density plasma (rippled density). For the resonant excitation of THz radiation the ripple wave number is suitably chosen to satisfy the phase matching condition. In this process, the lasers exert a ponderomotive force which imparts an oscillatory velocity to the electrons that couple with the density ripple to generate a stronger transient transverse current due to the spatial variation of their fields, driving THz radiation (with the frequency of the order of the plasma frequency). Various laser and plasma parameters were optimized and we report an efficiency of the order of ∼8 × 10−3 for the current scheme.