Directional Plasmonic Nano-Antennas

We address 2D arrays of metallic nano-particles arranged in a honeycomb lattice in the proximity of a hetero-interface of two media with high dielectric contrast. These systems can function as antennas in the visible range of the spectrum. We demonstrate that their radiation patterns can be made very directional by appropriate choice of the system geometry and materials. We show also that if such an antenna is excited by evanescent waves, the direction of the main radiation lobe can be switched abruptly by changing the polarization of the incident light. Within the proposed excitation scheme the device converts an incident plane wave into a narrow beam, operating as a nanoscopic source of light with tunable directionality.