Revealing Plasmonic Property Similarities and Differences Between a Nanoparticle on a Metallic Mirror and Free Space Dimer Nanoparticle

Conventionally, in plasmonics, experimentally developed nanoparticle on a metallic mirror design is used to mimic the free space dimer metallic nanoparticles. Numerous theoretical simulations considering free space dimer were carried out and their plasmonic properties were applied to nanoparticle on a metallic mirror design. In this work, with the help of three-dimensional finite element method simulation we directly compared the free space dimer and nanoparticle on a metallic mirror designs and analyzed their plasmonic properties. Although there are similarities in their generalized near field enhancement properties, we observe significant differences as well. With the help of three-dimensional surface charge density mappings, we explain the origin of these differences, as cross-sectional amplitude of electric field profiles has limitation in understanding such complex plasmonic mode(s). We hope our study will be helpful in understanding the origin of complex plasmonic modes, and sub-wavelength optical properties for the development of the efficient light devices.