Self-Focusing of Elliptical Laser Beam in Collisional Plasma and Its Effect on Stimulated Brillouin Scattering Process

This paper presents an investigation of self-focusing of elliptical laser beam in a collisional plasma and its effect on stimulated Brillouin scattering (SBS) process. The non-linearity arising through non-uniform heating leads to redistribution of carriers, which modifies the background plasma density profile in a direction transverse to pump beam axis. This modification affects the incident laser beam, ion-acoustic wave and back scattered beam. Non-linear differential equations for the beam width parameters of the pump laser beam, ion-acoustic wave and back scattered beam are set up and solved numerically. It is observed from the analysis that the focusing of waves greatly enhances the SBS back-reflectivity.