Approximate analytical solution of equation for effective radius of high-power femtosecond laser beam in the approximation of Gauss intensity profile at its self-focusing in the air is found. This equation was derived based on the equation for Wigner func-tion of laser radiation field in the developed optical turbulence conditions. Estimations for global self-focusing distance versus peak radiation power are presented as well as laser beam propagation coefficient characterizing its divergence after nonlinear focus.
femtosecond laser radiation, effective characteristics, optical turbulence