A light scattering model for large particles with surface roughness.

A physical-optics hybrid method designed for the computation of single-scattering properties of particles with complex shapes, including surface roughness, is presented. The method applies geometric optics using a novel ray backtracing algorithm to compute the scattered field on the particle surface. A surface integral equation based on the equivalence theorem is used to compute the scattered far-field, which yields the full Mueller matrix and integrated single-scattering parameters. The accuracy is tested against the discrete dipole approximation for fixed orientation smooth and roughened compact hexagonal columns for 3 values of refractive index. The method is found to compute asymmetry parameter, and scattering and extinction efficiencies with mean errors of − 1. 0 % , − 1. 4 % , − 1. 2 % , respectively, in a computation time reduced by 3 orders of magnitude. The work represents a key step forwards for modelling particles with physical surface roughness within the framework of physical-optics and provides a versatile tool for the fast and quantitative study of light scattering from non-spherical particles with size much larger than the wavelength. • Physical-optics hybrid light scattering code for large particles with roughness. • Novel ray back-tracing algorithm and vector diffraction theory at an aperture. • Far field obtained by sum of transmission, reflection, and external diffraction. • Simulation tool for 2-d scattered field and single-scattering parameter computation. [ABSTRACT FROM AUTHOR]