Ionisation refraction as the cause of space — time modulation of a short intense laser pulse

The three-dimensional dynamics of the propagation of a short intense laser pulse in an ionising material is analysed. The modulation of the temporal profile of the laser pulse caused by the essentially three-dimensional dynamics of its propagation is studied using an analytic model proposed. The criterion for realisation of various scenarios of the pulse propagation in an ionising gas is suggested. The numerical self-consistent analysis of the nonlinear propagation of the pulse in the ionising material showed the correctness of conclusions of the simplest analytic model.