Beam Spread of Laser Light Propagating in a Random Medium

TLDR: In this paper, the beam spread of laser light when it propagates in a random medium is analyzed in terms of the coherence function and it is shown that the irradiance pattern is always gaussian and that the characteristic beam diameter increases at a rate proportional to z32, where z is the propagation distance.

Abstract: We consider here the beam spread of laser light when it propagates in a random medium. The analysis is given in terms of the coherence function. Explicit results are obtained principally for the region of multiple scatter. In this region, it is shown that the irradiance pattern is always gaussian and that the characteristic beam diameter increases at a rate proportional to z32, where z is the propagation distance. The proportionality constant is determined for an arbitrary index-of-refraction spectrum, and the Kolmogorov spectrum is given as a special case. The results obtained are considered in atmospheric and oceanographic applications.