Directional and Polarized Emission from Nanowire Arrays.

Lighting applications require directional and polarization control of the emitted light, which is currently achieved by bulky optical components such as lenses, parabolic mirrors, and polarizers. Ideally, this control would be achieved without any external optics, but at the nanoscale, during the generation of light. Semiconductor nanowires are promising candidates for lighting devices due to their efficient light outcoupling and synthesis flexibility. In this work, we demonstrate a precise control of both the directionality and the polarization of the nanowire array emission by changing the nanowire diameter. We change the angular emission pattern from a large-angle doughnut shape to a narrow-angle beaming along the nanowire axis. In addition, we tune the polarization from unpolarized to either p- or s-polarized. Both the far-field emission pattern and its polarization are controlled by the number and type of guided or leaky modes supported by the nanowire, which are determined by the nanowire diameter.