Enhanced backscattering of polarized light from discrete random media : calculations in exactly the backscattering direction

Enhanced backscattering of polarized light by disordered media composed of independently scattering particles of arbitrary size and shape is studied theoretically. Rigorous relations between the cyclical and the ladder parts of the backscattering matrix in exactly the backscattering direction are derived for three commonly used representations of polarization, and the corresponding polarization backscattering enhancement factors are introduced. The ladder part of the Stokes-backscattering matrix is calculated by solving Chandrasekhar’s vector radiative transfer equation [ Radiative Transfer ( Clarendon, London, 1950)]. The general properties of the enhancement factors are studied, and the results of numerical computations are reported for finite and semi-infinite homogeneous slabs composed of spherical and randomly oriented nonspherical particles. It is shown that the enhancement factors depend strongly on the direction of light incidence, the optical thickness of the medium, the true absorption, and the particle size and shape.