The results of self-focusing influence of high-power femtosecond laser radiation on spatial energetic beam structure are presented. Experimental data on transversal distribution of energy density of sharply focused Ti:Sapphire laser after its filamentation in the atmosphere are given in this paper. Their interpretation was carried out based on the model of nonlinear Schrodinger equation. It is shown that the best agreement between theory and experiment when it is taking into account in the theoretic model of the character, changing nonlinear medium response, realized at high radiation intensity in nonlinear beam focus. It is seen in a change of multiphoton physical mechanism of molecule ionization on the tunnel with Kerr nonlinearity and in appearance of ionization saturation owing to medium nonlinearity of higher order.
laser radiation; self-focusing; filamentation; plasma; divergence