Self-focusing and defocusing of TEM0p Hermite-Gaussian laser beams in collisionless plasma

The authors have investigated the self-focusing and defocusing of first six TEM_0p Hermite-Gaussian laser beams in collisionless plasma. In case of collisionless plasma the nonlinearity in the dielectric constant is mainly due to the ponderomotive force. It is found that modes with odd p-values defocuses and that with even p-values exhibit oscillatory as well as defocusing character of beam-width parameters variation during their propagation in collisionless plasma. The entire theoretical formulation is established under parabolic wave equation approach. The numerical computation is completed by using fourth order Runge-Kutta method. Finally the behavior of beam-width parameters with the dimensionless distance of propagation is presented graphically.