Self-trapping and Self-focusing of a Non-gaussian Laser Mode in a Collisionless Plasma

In this paper the self-focusing of a laser beam has been studied in a collisionless plasma when the laser is operating in a TEM 10 mode. The critical power required for typical self-trapping of this mode is slightly more than that required for the lowest order mode and depends upon the eccentricity of the initial beam shape. The conditions of propagation are obtained for self-trapping and simultaneous self-focusing of both the dimensions of the beam. It is observed that stigmatic self-focusing around the points of irradiance maxima occurs only if there is a non-zero eccentricity in the cross-section of the beam.