Coupling of plasmonic gap waveguides with directive antennas

Optical nanocouplers matching a fiber microwaveguide to a plasmonic nanowaveguide are essential components for practical applications of nanophotonic systems. In this paper, an efficient nanocoupler operating at optical frequencies is designed that uses a directive nanoantenna to maximize the coupling efficiency (CE). Despite the reduced size of the nanoantenna in comparison with the impinging fiber spot size, we have shown that a good efficiency can be achieved, improving the CE by a factor of 10 with respect to the nondirective antenna nanocouplers.