Abstract

The paper deals with the structural instability of a focused high-power short laser pulse capable of producing rapid field-induced ionization of a dense gas. This is a key problem in proposed applications of intense subpicosecond lasers, including the creation of dense cold plasmas for X-ray lasing, the laser-driven particle acceleration schemes and the processes of laser frequency up-conversion. This problem has actively been discussed recently (see, e.g., [1-3]), but the main attention has been payed to the analysis of the defocusing properties of "smooth" emerging plasma objects. In our consideration the emphasis is layed on electrodynamics, or more precisely, on the joint evolution of the wave field and plasma for a specific nonlinearity law, assuming the field ionization (tunneling or multiphoton) rate for the issues of interest to be a known function of the field amplitude. As has been shown in a previous paper [4], strong electromagnetic waves propagating in media with ionization nonlinearity may cause the development of various types of ionization instabilities. The main role under the discussed conditions is played by the instability of the stimulated ionization scattering. We demonstrate that the dynamics of the interaction between ionizing short laser pulses and gases may be accompanied by the stimulated forward ionization scattering at small angles to the propagation direction, which completely changes the structural and temporal characteristics of the laser field and produced plasma.

© 1994 Optical Society of America