Equations for Electromagnetic Radiation Transfer in Dielectric Random Media with Effects of Near Fields and Opposite Wave Streams' Interference

Abstract

A radiative transfer theory for electromagnetic wave multiple scattering in dielectric random media with effects of near fields is presented. The theory is based on Sommerfeld-Weyl angular spectrum decomposition of wave amplitudes and technique of Dyson and Bethe-Salpeter equations for the ensemble averaged angular spectrum amplitudes and the coherence matrix of angular specrum amplitudes, respectively. We derive the four integral equations’ system, for two autocoherences of waves propagating forward and backward with respect to embedding parameter into the medium slab and two cross-coherences of evanescent waves decaying in opposite directions. In so doing the equations for autocoherences describe basically the usual radiative transfer with wave intensity multiple scattering by random inhomogeneities (scatterers) and free path between them. In the contrary the equations for cross-coherences demonstrate a new effect of elementary evanescent waves’ virtually exciting inside an inhomogeneity in pairs of opposite decaying derections and contribution of these evanescent pairs to wave energy flux.