In present study, Self-focusing of high power beam in unmagnetized plasma and its effect on Stimulated Raman scattering (SRS) process is investigated. Both relativistic-ponderomotive nonlinearities are taken together. Electron plasma wave (EPW) interacts nonlinearly with pump beam thereby leading to SRS. Under combined action of relativistic-ponderomotive forces, nonlinearity in plasma dielectric function is set up. These further causes change in plasma’s density profile in perpendicular direction to pump beam axis. This modification greatly influences input beam, scattered beam and EPW. Nonlinear differential equations for input beam, scattered beam and EPW are set up using Wentzel Kramers Brillouin approximation and paraxial theory. Numerical simulations are executed for analyzing effect of well-known parameters of laser and plasma medium on focusing/defocusing of various beams involved in the process and SRS back-reflectivity. It is confirmed that focusing of beams involved raises SRS back-reflectivity.

在本研究中，研究了未磁化等离子体中高功率光束的自聚焦及其对受激拉曼散射（SRS）过程的影响。相对论-脑机能动力学的两个非线性因素是一起考虑的。电子等离子体波（EPW）与泵浦光束非线性相互作用，从而导致SRS。在相对论-动力作用的共同作用下，建立了等离子体介电函数的非线性。这些进一步导致等离子体的密度分布在垂直于泵浦光束轴的方向上发生变化。这种修改极大地影响了输入光束，散射光束和EPW。使用Wentzel Kramers Brillouin逼近和近轴理论建立输入光束，散射光束和EPW的非线性微分方程。进行数值模拟以分析激光和等离子体介质的公知参数对过程中涉及的各种光束的聚焦/散焦以及SRS背反射的影响。可以确认，所涉及的光束的聚焦提高了SRS的背反射率。