Packed Yagi-Uda nano-antennas using a unidirectional feed at visible wavelengths.

Optical nano-antennas' capability for controlling the intensity and direction of freely propagating waves is a precursor to demanding on-chip optical communications. Here we present a novel and efficiently packed Yagi-Uda (P-YU) nano-antenna which is dramatically directive and shortened. This is due to the excitation of a pair of strong interacting Au nanorods as a feed in the form of conventional Yagi-Uda (YU). Using a sophisticated feed with a unidirectional radiation pattern in a wavelength close to the antiphase hybridized plasmon causes significant directionality in the designed nano-antennas' emission. This allows us to reduce the number of directors or overall size while directivity and gain of the P-YU antenna considerably improve at about 610 nm.