Enhancement of backscattered diffuse specific intensities from random distributions of finitely conducting particles with rough surfaces

Abstract

The incoherent diffuse specific intensities (modified Stokes parameters) backscattered from a horizontal layer consisting of random distributions of finitely conducting particles with smooth surfaces and finitely conducting particles with rough surfaces are evaluated. The normally and obliquely incident excitations at infrared and optical frequencies are vertically or horizontally polarized. The particle-surface roughness, which is characterized by its joint probability-density function, is assumed to be sufficiently rough to affect the diffuse specific intensities significantly. Thus the full-wave approach is used to determine the phase matrix as well as the extinction coefficient that appears in the equation of radiative transfer. The enhanced backscattered intensities that depend on the particle-surface roughness are compared with the enhanced backscatter that is associated with Mie scatter from smooth spherical particles. The enhanced backscattered diffuse specific intensities are evaluated for different particle sizes, complex permittivities, roughness parameters, and excitations. The effects of varying the optical thickness of the layer are also considered. Since the enhanced backscatter phenomenon reported here is primarily due to the particle-surface roughness, it appears in both the first-order solution and the multiple-scatter solution of the radiative-transfer equations.