Effect of dependent scattering on light absorption in highly scattering random media

Abstract

In the last a few decades, the approximate nature of radiative transfer equation (RTE) leads to a bunch of considerations on the effect of dependent scattering in random media, especially in particulate media composed of discrete scatterers. This effect usually indicates those deviations of RTE from experimental and exact numerical results due to electromagnetic wave interference. Here we theoretically and numerically demonstrate the effect of dependent scattering on absorption in disordered media consisting of highly scattering scatterers. By making comparisons between the independent scattering approximation-radiative transfer equation (ISA-RTE) approach and the full-wave coupled dipole method (CDM), we find that deviations between the two approaches increase as the scatterer density increases. The discrepancy also grows with the optical thickness of the whole random media. To quantitatively take dependent scattering effect into account, we develop a theoretical model of the dependent-scattering corrected radiative properties, based on the path-integral diagrammatic technique and the quasi-crystalline approximation (QCA) in the multiple scattering theory. The model results in a more reasonable agreement with numerical simulations. The present work is of practical importance in correctly modeling light absorptance in random media and interpreting the experimental observations in various applications for random media, such as solar energy concentration, micro/nanofluids, structural coloration, etc. It also has profound implications for the coherent scattering physics in random media with absorption.