Stimulated Raman scattering of elliptical laser beams in thermal quantum plasma

Theoretical investigation on the phenomenon of stimulated Raman Scattering (SRS) of an intense laser beam propagating through thermal quantum plasma has been presented. The source of scattering has been assumed to be a pre-excited electron plasma wave (EPW) propagating through the plasma. The nonlinear interplay between incident beam, EPW and scattered beam has been investigated in detail. Due to non-uniform irradiance over the cross section of the laser beam, the DC component of ponderomotive force becomes finite and redistributes the plasma electrons in plane transverse to the pump beam. Due to this redistribution of plasma electrons the plasma starts behaving as a nonlinear medium. The wave equations for the pump beam, EPW and scattered beam have been set up and solved semi analytically by moment theory approach. Particularly the dynamical evolution of backward reflectivity of plasma as a function of longitudinal distance has been investigated in detail. The effects of pump beam ellipticity and deviation of its irradiance from Gauussian distribution on SRS process have been incorporated. (author)