Probing nanoplasmonic waveguides and couplers with optical antennas

The authors report the first experimental realization of an optical antenna exciting a plasmonic gap waveguide (width ~ 80nm, antenna coupling efficiency from the far field to the waveguide ~ 15%. The high polarization sensitivity of the antenna in combination with a bent gap waveguide, which turns the polarization, allows us to probe nanoplasmonic devices with a high signal-to-noise ratio in the crossed polarization mode.