Two-stream theory of diffusing light spectroscopies

A theory for the propagation of light through a randomly scattering slab is developed that does not take advantage of a diffusion approximation but can be solved analytically. The treatment allows for scattering anisotropy and boundary reflectivity to be incorporated in a straightforward fashion for slabs of arbitrary thickness. Predictions are found for both the transmission probability and the electric field autocorrelation function which, respectively, can be used to analyze diffuse-transmission spectroscopy and diffusing-wave spectroscopy data more accurately.