Confined Mie Plasmons in Monolayer Hexagonal-Close-Packed Metallic Nanoshells

Using a double templating method by electroless deposition within a templating organic porous mold, we fabricate a monolayer of hexagonal-close-packed metallic nanoshells, each with a small opening. Light transmission spectra of the metallic nanoshell arrays are measured, which show transmission resonances at specific wavelengths whose positions are observed to be independent of the incident angle as well as light polarizations. More interestingly, the resonance wavelengths of Mie plasmon modes are also independent of the surrounding medium. Further numerical simulations confirm these transmission resonances and reveal that they are attributed to the excitations of highly localized dipolar, quadrupolar and hexapolar Mie plasmon modes, which are highly confined within metallic nanoshells.