Angular dependence of stimulated Brillouin scattering in a homogeneous two-dimensional plasma

The linear evolution of stimulated Brillouin scattering (SBS) in time and two spatial dimensions was studied analytically and numerically. In order to assess the effects that the finite size of the laser beam has on SBS, wide and narrow laser-beam geometries were considered. Detailed comparisons were made between the predictions of reduced one- and two-dimensional models, which can be solved analytically, and the results of two-dimensional numerical simulations. It was found that SBS is characterized by three parameters: the spatial growth rate in the direction of the Stokes wave, the spatial damping rate of the ion-acoustic wave in the direction of the Stokes wave, and the normalized width of the interaction region. The SBS can be saturated by the damping or the lateral convection of the ion-acoustic wave, both of which limit the growth of the ion-acoustic wave (directly) and the Stokes wave (indirectly). For most scattering angles the saturation mechanism predicted by the reduced models, and the corresponding saturation time and gain factor, agree with the simulation results. copyright 1999 American Institute of Physics