Light scattering by optically anisotropic scatterers: T-matrix theory for radial and uniform anisotropies.

Abstract

We extend the T-matrix approach to light scattering by spherical particles to some simple cases in which the scatterers are optically anisotropic. Specifically, we consider cases in which the spherical particles include radially and uniformly anisotropic layers. We find that in both cases the T-matrix theory can be formulated using a modified T-matrix ansatz with suitably defined modes. In a uniformly anisotropic medium we derive these modes by relating the wave packet representation and expansions of electromagnetic field over spherical harmonics. The resulting wave functions are deformed spherical harmonics that represent solutions of the Maxwell equations. We present preliminary results of numerical calculations of the scattering by spherical droplets. We concentrate on cases in which the scattering is due only to the local optical anisotropy within the scatterer. For radial anisotropy we find that nonmonotonic dependence of the scattering cross section on the degree of anisotropy can occur in a regime to which both the Rayleigh and semiclassical theories are inapplicable. For uniform anisotropy the cross section is strongly dependent on the angle between the incident light and the optical axis, and for larger droplets this dependence is nonmonotonic.