Intensity limitation and energy spreading in an optical field under transient thermal defocusing conditions

An experimental investigation was made of two new effects of transient thermal defocusing. These effects were the limitation of the peak intensity of the pulses and spreading of the energy in the optical field. In both effects an important quantity was the energy of a nonlinear precursor W_pr. The intensity limitation was observed when the energy of the leading edge was greater than W_pr. The spreading occurred when the energy of the whole pulse was greater than W_pr. The experiments were carried out for pulsed xenon radiation in an alcoholfilled cuvette. The calculation equations for these two effects were derived.