Light scattering by Gaussian random particles with discrete-dipole approximation

Abstract

We study scattering of light by Gaussian-random-sphere particles with sizes comparable to or slightly larger than the wavelength of incident light. Using an efficient computer code based on the discrete-dipole approximation, the scattering computations are carried out for a set of particle sizes, refractive indices, and statistical shape parameters. For the present mean-radius ( a) size parameters x = ka ∈ [ 1 , 7 ] ( k is the wave number), there are intriguing similarities and differences in scattering by spherical and Gaussian particles. However, we can summarize several ubiquitous results for scattering by Gaussian particles. First, for all cases studied, there is an increase toward backscattering in the scattering-phase-matrix element P 11 (phase function). Its angular width diminishes with increasing particle size. Second, in the degree of linear polarization for unpolarized incident light - P 21 / P 11 , there is a systematic negative polarization feature that is wider for larger refractive indices and smaller particle sizes. Third, P 22 / P 11 , equal to unity for spherical particles, shows a double-lobe feature in the backward-scattering regime. Fourth, when plotted two-dimensionally against the scattering angle and size parameter, - P 21 / P 11 shows positive islands and bridges at intermediate scattering angles. Physical mechanisms are suggested for the backscattering phenomena reported.