Simulation model for the effects of nonlinear polarization on the propagation of intense pulse lasers

A simulation model including the effects of nonlinear polarization of a background neutral gas on the propagation of intense short pulse lasers is presented. The model includes the finite response time of the gas by using a soft-core Coulombic potential for the bound electrons. A test problem for self-focusing of a pulse is presented. Agreement with theoretical predictions for the self-focusing of an intense laser pulse in a gas with a finite-response-time nonlinear polarization included is found.