Zinc Oxide nanowire gratings for light absorption control through polarization manipulation

Abstract

Light-matter interaction has recently become an intense area of research in the field of photonic devices. Absorption control in semiconductors plays an important role in device performance, especially for plasmonic waveguides. Zinc Oxide (ZnO) is a known material for many photonic applications, where nanowires show quantum confinement effects in the ultraviolet and visible ranges. For applications requiring high-efficiency coupling from single-photon emitters and in ultra-sensitive optical sensing devices, the confined modes are highly desired. This is because surface plasmons enable the confinement and transport of light in highly-sub-wavelength volumes. In this study, we report a theoretical investigation of the change in absorption of intrinsic ZnO at the ZnO-silicon interface by a collimated light at variable incident angles. A confined wave or the weak plasmonics wave is created in the boundary region with a zone radius of 20 nm. The incident center wavelength is selected as 367 nm, which corresponds to the maximum absorption peak of the ZnO. The results show highly polarization dependent ZnO nanowire-silicon absorption, where the transmittance and reflectance vary with changes in the incident polarization. The confined electric field within the structure can be enhanced further by increasing the input power which varies between 1 and 5 W. An electric field of 1.4 × 105 V/m is confined within a small zone, where high transmittance (for incident angles smaller than 80°) and reflectance (for the incident angles greater than 80°) are demonstrated for the zeroth-diffraction order. Consequently, the minimum absorption loss within the configuration occurs for the zeroth-diffraction order.