Gaussian beam characterization for laser beam propagation through translucent, multi-layer medium with random indices of refraction

In this paper, a new model for characterizing short-range, free-space optical channels for the weak-turbulence scenario is proposed. The turbulence is attributed to fluctuations in the index of refraction. The proposed model assumes a multi-layer optical propagation medium where each layer may be divided into a large number of sub-layers. Furthermore, each sub-layer is assumed to possess an index of refraction that is random with an unknown probability density function (pdf) unique to that sub-layer. Further, it is assumed that the propagation losses, such as scattering and absorption, are negligible. That is, the losses are limited to the geometric loss. Using the ABCD matrix for the proposed channel, the statistical properties of a Gaussian beam, such as beam waist and radius of curvature, are studied. It is shown that for large propagation distances, the above parameters assume Gaussian characteristics.