Abstract: A plasmonic coupling device (1) comprising a first structure (2), and a second structure (3) comprising two or more conductive nanoparticles (7), wherein each nanoparticle is elongate and is attached to the first structure such that it is oriented with a major axis thereof substantially perpendicular to the first structure. In a plasmonic coupling device comprising such nanoparticles, radiation incident on the device can produce localised surface plasmons in the nanoparticles. The localised surface plasmons can become deiocalised along the device, due to the near-field electromagnetic interaction between the two or more nanoparticles or between the one or more nanoparticles of an assembly and a nearby assembly or assemblies. This interaction allows for electro-magnetic energy, and the radiation, to be efficiently coupled between the nanoparticles or between the assemblies of one or more nanoparticles.

Abstract: A surface plasmon element comprising an array of metal nanoparticles (1) with an adsorbed layer of resonant material and the use of such material to activate said array.