Directional control of light by a nano-optical Yagi-Uda antenna

The plasmon resonance of metal nanoparticles can direct light from optical emitters in much the same way that radio-frequency antennas direct the emission from electrical circuits. Recently, rapid progress has been made in the realization of single-element antennas for optical waves(1-12). Because most of these devices are designed to optimize the local near-field coupling between the antenna and an emitter, the possibility of modifying the spatial radiation pattern has not yet received as much attention(13,14). In the radiofrequency regime, a typical antenna design for high directivity is the Yagi-Uda antenna, which essentially consists of a one-dimensional array of antenna elements driven by a single feed element. By fabricating a corresponding array of nanoparticles, similar radiation patterns can be obtained in the optical regime(15-18). Here, we present the experimental demonstration of directional control of radiation from a nano-optical Yagi-Uda antenna composed of appropriately tuned gold nanorods.