Growth and stabilization of a laser ripple on laser beam in a collisionless unmagnetized plasma

Abstract

In this paper we have studied the growth and stabilization of a radially symmetric ripple superimposed on a laser beam in a collisionless unmagnetized plasma. The saturation of the growth rate is due to pump depletion effect. On acoount of the nonuniform intensity distribution of the main beam, a d.c. component of the ponderomotive force becomes finite and it redistributes the carriers in the plasma in a plane transverse to the beam propagation. We have set up and solved the wave equations for main beam and ripple by using the WKB and paraxial ray approximations. As the ripple grows in the plasma, it draws energy from the background laser field. It is seen that the relative intensity of the laser ripple becomes critical due to the counteracting behaviour of the self-focusing and depletion of the main beam.