Filamentation of laser beams and excitation of ion acoustic wave in non-paraxial region

This paper contains the work on the filamentation of a laser beam and its effect on excitation of ion acoustic waves in a hot collision less plasma in non-paraxial region. To consider the non-paraxial region, the amplitude and the eikonal part of the beams are expended in terms of r(2) and r(4). On account of the non-uniform intensity distribution along the wave front of the laser beam, the ponderomotive force becomes finite. This leads to modification of the plasma density profile in the plane transverse to the beam axis and hence also the modification in the propagation characteristics of the waves propagating in the plasma. It is shown that the Filamentation of the waves can occur and this considerably affects the ion acoustic wave.