Electron plasma wave excitation by self-focused cosh gaussian laser beams in axially inhomogeneous plasma: effect of density ramp

Dynamics of the laser driven electron plasma waves (EPWs) in plasmas with axial density ramp has been investigated theoretically. The effect of self focusing of the laser beam on the power of laser excited EPW has been incorporated. During its propagation through the plasma, the laser beam excites an EPW at frequency omega(ep) that due to the optical nonlinearity of plasma gets nonlinearly coupled to the laser beam due to the ponderomotive nonlinearity of plasma electrons. Using variational theory semi analytical solutions of the coupled nonlinear wave equations for the pump wave and EPW have been obtained under W.K.B approximation technique. It has been observed that power of the EPW is significantly affected by the self-focusing effect of pump beam.