Nonlinear propagation characteristics of multi-Gaussian beams in collisionless plasmas

The nonlinear propagating characteristics of multi-Gaussian beams in homogeneous and inhomogeneous collisionless plasmas are theoretically explored. A differential equation of the dimensionless parameter associated with beam width is derived using the Wentzel–Kramers–Brillouin method and paraxial ray theory, and the relative beam width and intensity along the direction of propagation are determined. The dependence of the beam spot on eccentric displacement, initial beam intensity, incident beam frequency, and electron density is studied and compared. For inhomogeneous plasmas, electron density increases or decreases, and is modeled by the tanh function. The characteristics of unstable oscillation are presented and discussed.