Nonlinear propagation of laser radiation in an inhomogeneous plasma

A high-power Gaussian laser beam propagating at an angle to the density gradient in a plasma suffers from three effects: (1) size reduction due to curvature in the ray trajectories, (2) size enhancement due to diffraction divergence, and (3) size reduction due to self-focusing. The authors have incorporated these three competing processes in the wave equation and solved it analytically. It is seen that as the beam approaches the reflection layer, its intensity decreases due to the predominance of diffraction effects as against the prevailing belief of intensity enhancement due to curvature in the ray trajectories.