Spatial coherence of random light beams subject to thermal self-interaction

A study is made of the propagation of partly coherent high-power light beams in absorbing media. A report is given of the first experimental observation of a reduction in the correlation radius on increase in the radius of a random beam, caused by thermal self-defocusing. The results are given of a determination of the dependence of the correlation radius on the beam power and on the absorption coefficient of the medium traversed by the beam. A theoretical analysis of the self-interaction of random beams is made by the method of integration over beam paths, based on a new technique in which it is postulated that a random beam creates a randomly inhomogeneous channel in a nonlinear medium and travels along this channel. The results of this theory are in agreement with some experimental data.