Optical Nanoantennas Coupled to Photonic Crystal Cavities and Waveguides for Near-Field Sensing

The performance of dipole nanoantennas coupled to two different waveguides, a cylindrical waveguide and a photonic crystal waveguide, illuminated with a polarized electromagnetic wave incident from the air and from the substrate is analyzed by numerical simulations. When illuminated from the air, the photonic crystal waveguide antenna showed two resonances spectrally far apart from each other: one of them corresponds to the main antenna resonance and the other one to the modes excited in the photonic crystal cavity. The cylindrical waveguide antenna shows only the main antenna resonance. No significant antenna response was observed at a polarization perpendicular to the main axis of the antenna. Illumination from the substrate did not increase the response of the waveguide-coupled antenna. These results show that antenna-coupled waveguides could be used as detectors for near-field applications where polarization sensitivity and dual band operation are desired.