Substrate effects on the optical properties of spheroidal nanoparticles

We developed a spectral formalism to study the effective polarizability of a spheroidal particle lying over a substrate, including multipolar effects. With the help of the spectral representation, we can discuss the optical response in terms of the excitation of the multipolar modes of the system. As an example of applications, we provide a spectral representation of the differential-reflectance spectra and we perform calculations for specific systems.