Excitation of Dark Plasmons in Metal Nanoparticles by a Localized Emitter

We study theoretically a dipole emitter placed near a metal nanoparticle and near small chains of two and three nanoparticles. The emitter can efficiently excite dark, or nonradiative, surface-plasmon modes in the nanostructures, in addition to the well-known bright modes. In the case of coupled nanoparticles, the origins of the bright and dark modes can be understood in the context of plasmon hybridization. Excitation of dark modes in nanoparticle chains allows for subwavelength guiding of optical energy with no radiative losses and thus with improved propagation lengths.