General Scattering Characteristics of Resonant Core–Shell Spheres

This paper presents and discusses the general features and aspects regarding the electromagnetic scattering by a small Core-Shell plasmonic sphere. First, the thickness effects on the plasmonic resonances are presented in the electrostatic (Rayleigh) limit, utilizing the MacLaurin expansion of the Mie coefficients of hollow scatterers. Several aspects regarding the core effects are given, illustrating the enabling mechanisms and peculiarities of its resonant scattering response on the electrostatic limit. The electrodynamic aspects of the scattering process are revealed through the newly introduced Padé expansion of the Mie coefficients. Additionally, we expose how the core material affects the dynamic mechanisms, such as the dynamic depolarization and radiative damping. The described method can be expanded for other types of resonances and canonical shapes, while the general characteristics presented here are expected to stimulate further studies regarding the functionalities of the core-shell scatterers.