ION WAVE RESPONSE TO INTENSE LASER-BEAMS IN UNDERDENSE PLASMAS

Numerical and theoretical studies of laser beam interaction with under dense plasmas involving ion wave instabilities are presented. The theo retical model that is used involves realistic distribution of laser in tensity in a focal spot and a non-paraxial electromagnetic wave equati on coupled to the ion acoustic wave equation in a two-dimensional geom etry. Included among the important results is a weak correlation betwe en backscattered stimulated Brillouin scattering (SBS) reflectivity an d filamentation or self-focusing instabilities. The transmitted Light demonstrates angular spreading and frequency shifts consistent with ne ar-forward SBS. The role of filamentation and self-focusing on the tra nsmitted light is also discussed. (C) 1997 American Institute of Physi cs.