Stimulated Brillouin scattering of a short pulse laser in a self-induced plasma channel

Abstract

An intense short pulse laser with Gaussian radial profile of intensity propagating through homogeneous plasma depletes electrons from the axial region due to the radial ponderomotive force, leaving ions immobile. The resulting electron density profile and relativistic mass nonlinearity aid the laser to propagate self-guided, overcoming diffraction divergence with minimum spot size, few times of c/ωp, where c is the velocity of light in vacuum and ωp is the plasma frequency at equilibrium. The laser undergoes stimulated Brillouin backscattering in the self-induced plasma channel. As the ratio of the oscillatory electron velocity to the velocity of light, |v0|/c exceeds 0.1, the ion acoustic wave goes over to a reactive quasimode with large growth rate, comparable to ion plasma frequency. The nonlocal effects due to high intensity laser play a major role in the growth rate of the ion acoustic reactive quasimode. In a plasma of 5 KeV electron temperature, the largest value of the growth rate occurs at a plasma density n00≅0.6ncr, where ncr is the critical density.