Exponential density transition based self-focusing of Gaussian laser beam in collisional plasma

Abstract

In this work, nonlinear aspects of a high intensity Gaussian laser beam propagating in plasma having upward density ramp of tangent and exponential profiles are studied. We have employed the nonlinearity in dielectric function of plasma due to nonuniform heating of carriers along the wavefront of the laser beam which is important in collisional plasmas. The differential equation governing the dimensionless beam width parameter is achieved by using Wentzel–Kramers–Brillouin (WKB) and paraxial approximations and solved it numerically by using Runge-Kutta fourth order method. Effect of exponential density ramp profile on self-focusing is systematically carried out and compared with tangent density ramp profile. It is found that exponential plasma density ramp causes the laser beam to become more focused than tangent density ramp over several Rayleigh length and gives reasonably interesting results.