Study of Spatial Characteristics of Laser Radiation Beam in Near-Field Zone in Its Nonlinear Interaction with Medium of Propagation

The self-defocusing of a powerful laser beam in its nonlinear interaction with the medium of propagation is considered. A technique of calculating the transformation of the cross section diameter and the radiation beam divergence as a result of interaction is set forth which is based on presentation of the medium layer as a sequence of thin thermal lenses. The boundary conditions for using the technique are formulated. The calculations are given, and the results of transformation of the CO-laser radiation beam during its propagation in the atmosphere are analyzed.