Localised plasmons in gold photonic nanocavities

Summary form only given. We demonstrate a simple scheme to produce large-area coloured metal surfaces by completely confining surface plasmons inside gold spherical nanocavities. Previous work on photonic metals has focused on the use of regular arrays of corrugations or holes of a lateral size much less than the optical wavelength which produces complex and highly directional performance due to their periodicity. In contrast to periodic patterning which produces photonic crystals for travelling waves, the negative nanocavity curvature here localises the electromagnetic fields into small volumes which can be arranged non-periodically. Thus, plasmons trapped in spherical voids arranged in amorphous arrays possess simple discrete energy levels.