VOLUME CURRENT METHOD FOR MODELING LIGHT-SCATTERING BY INHOMOGENEOUSLY PERTURBED SPHERES

A volume current method (VCM) for calculating the optical scattering b y inhomogeneous spheres is presented. The method is applicable to sphe res having small refractive-index perturbations. In this method the in ternal and scattered fields are approximated with a separation-of-vari ables solution, in which each mode has its own effective-average refra ctive index. These fields generate an additional volume polarization c urrent in the regions where the refractive index differs from the aver age refractive index of the sphere. The fields radiated by these polar ization currents are then added to the approximate fields radiated by the unperturbed sphere. When they are tested with off-centered layered spheres, the fields calculated with the VCM compare well with those f ound with separation of variables so long as the changes in the refrac tive index are small. When the host sphere is near resonance and the p erturbation is in a region where the resonant fields are large, the pe rturbations must be smaller than when the sphere is off resonance.