Nonlinear propagation characteristics and ring structure of a Gaussian beam in collisionless plasmas with high order paraxial ray theory

Abstract Nonlinear propagation characteristics of a Gaussian beam in collisionless plasma are studied by the high order paraxial ray theory. The ponderomotive nonlinearity is considered as the focus mechanism. To solve the problem of energy non-conversation, we improve the propagation formula for Gaussian beam. The propagation characteristics of the dimensionless beam-width parameter, relative beam intensity and spatial electron density are numerically studied and discussed. It is found that the ring structure emerges from Gaussian beam in the case of self-focusing regime, and the initial laser parameters play important parts on the intensity and location of ring structure. Moreover, the wave-packet oscillation modes of beam width and intensity are presented.