Sharif Digital Repository

The resonant vortex terahertz beam generation by the cross-focusing of two twistedcoaxial laser beams is investigated. For the resonant excitation of terahertz radiation,the rippled density in plasma and the ripple wave number is suitably chosen to satisfy thephase matching condition. The nonlinear current density at terahertz frequency arises dueto the spatial variation of two Laguerre-Gaussian coupled field. The terahertz intensityscales as the ponderomotive force of laser beams which imparts an oscillatory velocity tothe electrons and, in fact, input Laguerre-Gaussian laser beams properties such as vortexcharge number and beam waist. Various laser and plasma parameters are employed to...