Analysis of the Intensity Range for Self-Focusing of Bessel–Gauss Laser Beams in Plasma

We study the propagation dynamics of zeroth-order Bessel–Gauss laser beams in plasma in the relativistic ponderomotive regime of interaction. Based on the paraxial and Wentzel-Kramers-Brillouin approximations, we derive the nonlinear evolution equation governing the laser beam width parameter, in view of the parabolic equation approach. We predict the range of intensity for self-focusing of Bessel–Gauss laser beams with increase in plasma electron temperature. While analyzing the condition for self-trapping of Bessel–Gauss beams, we point out and discuss three regimes characterized by steady divergence, self-focusing, and oscillatory divergence of the laser-beam propagation in plasma. In particular, we consider the effect of the transverse component of the wave parameter in exploring the intensity range for self-focusing. The intensity range for self-focusing of Gaussian beam in the considered regime of interaction with plasma is also deduced as a particular case in our work.