Plasmon nanoparticle array waveguides for single photon and single plasmon sources.

This Letter discusses how linear coupled plasmon particle arrays inspired by radio frequency Yagi-Uda antennas can be used to construct both efficient unidirectional single photon sources and efficient directional single plasmon sources. Calculations using an exact multipole expansion method are presented of the spontaneous emission directivity, efficiency, and spontaneous emission decay rates, taking into account material loss in real noble metals. An analysis of the emission properties in terms of the dispersion relation of infinite arrays reveals how one can use guided mode dispersion to achieve desirable figures of merit. The key ingredient is to couple the source to array eigenmodes that are just beyond the light line but still wave vector matched to propagating modes to within the momentum uncertainty set by the inverse antenna length. Finally, this Letter shows that the emission decay rates can be controlled independently of the directionality and without penalty in quantum efficiency.