The influence of a self-focused laser beam on the stimulated Raman scattering process in collisional plasma

The influence of a self-focused beam on the stimulated Raman scattering (SRS) process in collisional plasma is explored. Here, collisional nonlinearity arises as a result of non-uniform heating, thereby causing carrier redistribution. The plasma density profile gets modified in a perpendicular direction to the main beam axis. This modified plasma density profile greatly affects the pump wave, electron plasma wave (EPW) and back-scattered wave. The well-known paraxial theory and Wentzel–Kramers–Brillouin approximation are used to derive second-order ordinary differential equations for the beam waists of the pump wave, EPW and the scattered wave. Further to this, the well-known fourth-order Runge–Kutta method is used to carry out numerical simulations of these equations. SRS back-reflectivity is found to increase due to the focusing of several waves involved in the process.