Hybrid Semiconductor Nanowire–Metallic Yagi-Uda Antennas

We demonstrate the directional emission
of individual GaAs nanowires by coupling this emission to Yagi-Uda
optical antennas. In particular, we have replaced the resonant metallic
feed element of the nanoantenna by an individual nanowire and measured
with the microscope the photoluminescence of the hybrid structure
as a function of the emission angle by imaging the back focal plane
of the objective. The precise tuning of the dimensions of the metallic
elements of the nanoantenna leads to a strong variation of the directionality
of the emission, being able to change this emission from backward
to forward. We explain the mechanism leading to this directional emission
by finite difference time domain simulations of the scattering efficiency
of the antenna elements. These results cast the first step toward
the realization of electrically driven optical Yagi-Uda antenna emitters
based on semiconductors nanowires.