Full-wave electromagentic analysis of a plasmonic nanoparticle separated from a plasmonic film by a thin spacer layer

This paper presents a theoretical analysis of the electromagnetic response of a plasmonic nanoparticle-spacer-plasmonic film system. The physical system consists of a spherical nanoparticle of a plasmonic material such as gold or silver over a plasmonic metal film and separated from the same by a dielectric spacer material. This paper presents a complete analytical solution of the Maxwell's equations, to determine the optical fields near the gold nanoparticle. It was found that the electromagnetic fields in between the plasmonic nanoparticle and the plasmonic film are extremely sensitive to the spacing between the nanoparticle and the film. This could enable the use of such a system for various sensing applications. The non-local nature of the plasmonic medium was also included in our analysis and it's effect on the resonances of the system was studied. The analytical solution was compared with an independent numerical method, the Finite Difference Time Domain (FDTD) method, to demonstrate the accuracy of the solution.