MULTIPLE RAYLEIGH-SCATTERING OF ELECTROMAGNETIC-WAVES

Multiple scattering of polarized electromagnetic waves in diffusive me dia is investigated by means of radiative transfer theory. This approa ch amounts to summing the ladder diagrams for the diffuse reflected or transmitted intensity, or the cyclical ones for the cone of enhanced backscattering. The method becomes exact in several situations of inte rest, such as a thick-slab experiment (slab thickness L much greater t han mean free path l much greater than wavelength lambda). The present study is restricted to Rayleigh scattering. It incorporates in a natu ral way the dependence on the incident and detected polarizations, and takes full account of the internal reflections at the boundaries of t he sample, due to the possible mismatch between the mean optical index n of the medium and that nl of the surroundings. This work does not r ely on the diffusion approximation. It therefore correctly describes r adiation in the skin layers, where a crossover takes place between fre e and diffusive propagation, and vice-versa. Quantities of interest, s uch as the polarization-dependent, angle-resolved mean diffuse intensi ty in reflection and in transmission, and the shape of the cone of enh anced backscattering, are predicted in terms of solutions to Schwarzsc hild-Milne equations. The latter are obtained analytically, both in th e absence of internal reflections (n = n(1)), and in the regime of a l arge index mismatch (n/n(1) much less than 1 or much greater than 1).