Mean energy distribution and averaged pattern of optical vortices of a partially coherent light beam propagating in a randomly inhomogeneous atmosphere

Abstract

Spatial evolution was studied of energy and phase distribution of a fluctuating laser beam carrying an optical vortex. Fluctuations of the optical field were induced by fluctuations of the generator parameters or by random variations of the index of refraction in a thin layer of the atmosphere represented by a phase screen. It was shown that vortex-like flow of energy typical for a coherent beam manifests itself in averaged characteristics of a partially coherent beam. Particularly, the mean tilt of the wavefront can be represented as a sum of the vortex and potential components, while the circular flow of energy is influenced mainly by the rotor of the vector field of wavefront tilts. As it turned out, after the phase screen having a quadratic structure function of fluctuations the vector filed of energy flow is formed with the vortex component corresponding to the model of fluid current known as Scully's vortex. The potential component of the filed induces focusing of the beam. This results in the gradual annihilation of the vortex in the far filed.