Abstract

The self-channeling of intense ultrashort laser pulses in plasmas is a subject of much current interest because of its potential use for producing extended regions of laser-plasma interaction. There are two kinds of nonlinear processes in plasmas, the electron expulsion out of the focal region due to the ponderomotive forces and the relativistic increase of the electron mass, which may be useful for the ultrashort pulse channeling. These effects act to increase the refractive index in the plasma where the light radiation is most intense and therefore form a focusing lens for the radiation. Our aim is to demonstrate that the self-channeling may occur in an other situation when intense laser pulses propagate in dense gases, producing rapid ionization. Indeed, recent experimental results,^1,2 where short-pulse self-channeling has been observed over distances of several Rayleigh lengths, have shown that a strong ionization does not destroy the guiding effect. We show that the interplay between the Kerr-type and the fast ionization nonlinearities may result in the formation of extended steady-state plasma-field structures where the guiding along the created plasma filament is attained due to the gas ionization.

© 1995 IEEE