Prospects of resonant optical antennas for nano-analysis

Suitably shaped metal nanostructures act as resonant optical antennas that efficiently collect light and confine it to a subwavelength volume. Vice versa, light emission from nano volumes can be enhanced by coupling to antenna structures. We give a short introduction to antenna theory and discuss recent experiments that show the feasibility of achieving strong field enhancement using resonant dipole antennas for near infrared wavelengths. By scanning an optical antenna fabricated at the apex of an AFM tip over individual quantum dots, we observe enhanced emission of the latter while it is in close proximity of the antenna feed gap. Resonant optical antennas hold promise to be applied for spectroscopic characterization of nano structures with high spatial resolutions and single-molecule sensitivity.