Study of optical properties of a plasmonic nanoparticle on a dielectric substrate

By studying the polarizability of a spherical metallic nanoparticle on a dielectric substrate, the optical properties of the system is investigated. Since the size of nanoparticle is much smaller than the wavelength of the incident light, by solving the Laplace equation, the electric potential at different regions is expanded in terms of multipoles. By using the polarizability tensor, expressions for the parallel and normal polarizability are derived and then numerical results discussed. In addition to the impact of the size of plasmonic nanoparticle, by defining a geometrical parameter that called the truncation parameter, the impact of this parameter on the parallel and normal components of polarizability tensor is shown. It is demonstrated that the optical dispersion and absorption strongly depends on the particle size, the type of metal particle and the truncation parameter. The type of nanoparticle is gold and silver, because these noble metals have predominately been the materials of choice for plasmonic applications around the optical frequencies.