Nonlinear Dynamics of Intense Laser Beam in Unmagnetized Plasma and its Influence on Second Harmonic Generation

The objective of present research is to explore nonlinear dynamics of intense laser beam in unmagnetized plasma and its influence on second harmonic generation (SHG). Here, collisional nonlinearity is considered. The plasma electrons get redistributed due to non-uniform heating in collisional plasma leading to production of density gradients in transverse direction. This further leads to electron plasma wave (EPW) excitation at the input frequency of beam. Excited EPW nonlinearly interacts with input beam thereby producing second harmonics. Nonlinear differential equation for beam waist of input beam and SHG yield are derived by making use of moment theory approach. The well accepted laser-plasma parameters are utilized for obtaining numerical solutions of these equations. The improvement in focusing behavior of beam and SHG yield is found with increment in density of plasma and radius of beam and also with decrease in intensity of beam. The outcome of this work is supportive in knowledge of laser-plasma interaction physics.