Temporal coupled-mode theory for light scattering by an arbitrarily shaped object supporting a single resonance

摘要

We develop a temporal coupled-mode theory to describe the interaction of plane wave with an individualnscatterer having an arbitrary shape. The theory involves the expansion of the fields on cylindrical or sphericalnwave basis for the two-dimensional and three-dimensional cases, respectively, and describes the scattering processnin terms of a background scattering matrix and the resonant radiation coefficients into different cylindrical ornspherical wave channels. This theory provides a general formula for the scattering and absorption cross sections.nWe show that for a subwavelength asymmetric scatterer with a single resonance, the scattering and absorptionncross sections can exceed the single-resonance limit for some specific incident angles of illumination, but thensum of these cross sections over all angles has an upper limit.We validate the theory with numerical simulationsnof a metallic scatterer that does not have any rotation symmetry.