Pole-zero analysis of scattering resonances of multilayered nanospheres

Abstract

We demonstrate a general pole-zero method for the design of the scattering resonances of multilayered nanospheres, and we apply it to the relevant cases of strongly dispersive light scattering from metal-dielectric-metal and all-dielectric nanostructures. The pole-zero method is based on the full-wave iterative solution of the Mie scattering theory of multilayered spheres, which is valid beyond the conventional quasistatic limit. By investigating scattering resonances in the complex frequency plane, we show how to engineer anomalous Fano-like dipolar line shapes from complex pole-zero interactions controlled by the geometrical parameters of the structures. The pole-zero method is then applied to the design of the backscattering and forward-scattering efficiencies beyond the dipolar approximation. The engineering of scattering and absorption resonances with customized line shapes in metal-dielectric nanostructures provides unique opportunities for active devices including optical sensors, light emitters, and nonlinear elements.