Spectral changes in inhomogeneous media depending on the spatial coherence of the source can be described by a quasi-optical approach. Assuming a Gaussian-Schell model source the spectral changes are described by using a Gaussian beam and ABCD matrices for the propagation in the medium.
Description:
R. Zwiggelaar and M.G.F. Wilson, 'Spectral changes in inhomogeneous media; a quasi-optical approach', Int. J. Infrared Millimeter Waves 14 (10), 2253-2259 (1993)