Abstract
We design a coupled plasmonic nanostructure, which consists of a Ag rhombus nanoparticle positioned over a silver film, separated by a dielectric spacer layer, and perform numerical analysis by calculating the radiation loss resistance of this nanostructure as the perfect electric conductor metal based on the theory of transmission line modes. Compared with the nanocube or triangular nanodisk film-coupled plasmonic nanostructures introduced in the previous works, a stronger electric field enhancement was achieved in the Ag rhombus nanoparticle film-coupled nanostructure because of the fact that the sharp tip of the rhombus nanoparticle can generate field enhancement at a hot spot. In order to demonstrate that the sharp tip can confine the electromagnetic energies strongly, we also have calculated the Purcell factor and the far-field directivity of the quantum emitter in the vicinity of this nanostructure.