Enhanced Brillouin scattering of gaussian laser beam in collisional plasma: Moment theory approach

In the present paper, enhanced Brillouin scattering of a gaussian laser beam in a collisional plasma has been investigated with the help of moment theory approach. The pump wave (omega(0), k(0)) interacts with pre-excited ion-acoustic wave (omega, k), thereby generating a back-scattered wave (omega(0) - omega, k(0) -k). As a specific case, back scattering for which k similar or equal to 2k(0) has been discussed. Due to nonuniform heating, collisional nonlinearity arises, which leads to redistribution of carriers. As a result background plasma density profile in a direction transverse to pump beam axis is modified. Consequently, the pump beam becomes self-focused and in turn leads focusing of ion-acoustic wave and back-scattered wave under appropriate conditions. It is further observed from the analysis that focusing of waves greatly enhances the SBS back-reflectivity.