Fano resonance by symmetry breaking in silver-silica-gold multilayer nanoshells

The multilayer nanoshells symmetry breaking makes otherwise dark higher order modes visible and interacting with the dipole mode. Fano resonance could be accomplished through interferences between these modes. Here we propose a structure based on three shells of different materials (silver, silica and gold) and study the near and far field optical properties. The resonant peaks of extinction and near field enhancement can be tuned and enhanced by offsetting the layers compared to the concentric geometry nanoshell respectively. By displacing the silica shell from the center, higher order dark modes appear in the spectrum predominantly compared to the silver-core and the outer gold-shell offset.