Color-switched directional ultracompact optical nanoantennas

We report on directionality of a novel optical nanoantenna composed of three gold nanodisks ultracompactly arranged in the end-fire configuration. It is found that the emission of a local light source can be remarkably directed and switched based on its color between two opposite directions. The quasi-static approximation is employed to theoretically model the optical properties of the nanostructure and to investigate the observed phenomenon. The proposed nanoantenna enhances and directs the yellow-color toward the forward-direction, and, in contrast, the red-color toward the backward direction. This unique color-switching property is studied in terms of the strong plasmonic interactions of the nanodisks and the resulting hybridized modes of the nanoantenna.