Effect of Self Focusing on Stimulated Raman Scattering of Elliptical 𝑞-Gaussian Laser Beam in Underdense Plasma with Axial Density Ramp
Naveen Gupta, Sanjeev Kumar and S.B. Bhardwaj
Stimulated Raman scattering (SRS) of elliptical 𝑞-Gaussian laser beams interacting with axially inhomogeneous plasmas has been investigated theoretically. An intense laser beam with frequency ω0 propagating through plasma gets coupled with a preexisting electron plasma wave (EPW) at frequency ω𝑒𝑝, due to ponderomotive nonlinearity on plasma electrons exerted by the laser beam. This nonlinear interaction of pump beam with EPW produces a back scattered wave at frequency ω𝑠 = ω0−ω𝑒𝑝. Using variational theory semi analytical solutions of the coupled nonlinear wave equations for the three waves (pump, EPW and scattered) have been obtained under W.K.B approximation technique. It has been observed that self focusing of the laser beam significantly affects the power of back scattered wave.