Equiphase-sphere approximation for light scattering by stochastically inhomogeneous microparticles.

We report the development and validation of the equiphase-sphere (EPS) approximation for calculating the total-scattering cross-section (TSCS) spectra of inhomogeneous microparticles having complex interior structures. We show that this closed-form, analytical approximation can accurately model the TSCS of randomly inhomogeneous spherical particles having internal refractive index variations with geometrical scales spanning from nanometers (i.e., subwavelength) to microns (i.e., suprawavelength). Moreover, we derive an easy-to-use criterion for the range of validity of the EPS approximation in modeling TSCS of inhomogeneous particles. The work discussed in this paper may positively impact tissue optical imaging and diagnostic applications.