Numerical and experimental simulation of the thermal selfaction of laser beams over a path in a medium moving at a variable velocity

A two-layer model of an inhomogeneous medium is used in a study of the influence of a change in the transverse component of the velocity of wind on the nonlinear thermal effects (defocusing and refraction). Numerical calculations and experimental results show that over short paths (less than two thermal self-interaction lengths) a change in the wind direction has the greatest influence on the beam displacement. The maximum intensity in the beam and its area can then be estimated using formulas for a homogeneous medium. Experiments show that over longer paths the defocusing of a beam may be quite different compared with that in a homogeneous medium.