Deep-ultraviolet to mid-infrared polarizers by Al nanowire metamaterials

Polarizers are one of the most fundamental elements used in optical devices. Compared with conventional prism polarizers, wire grid polarizers have potential for the miniaturization and integration of the optical devices. There are growing demands for design of the wire grid polarizers operating in a very broad spectral range from deep-ultraviolet to mid-infrared wavelengths. However, construction of the ultrabroadband polarizers based on the same structures and materials is very challenging. Here, ultrabroadband optical polarizers working in the deep-ultraviolet to mid-infrared spectral region, based on Al nanowire metamaterials with hexagonally packed nanowire arrays, are presented. To synchronously obtain high extinction ratios and low insertion losses, a q factor is found, when the q factor is fixed, the extinction ratio increases and the insertion loss simultaneously decreases with decreasing nanowire diameter. Moreover, the cut-off wavelength of the polarizers remarkably shifts to a much shorter wavelength when the refractive index of the surrounding medium decreases. Consequently, the polarizers demonstrate high performance operating down to the deep-ultraviolet spectral range based on an optimal design of the Al nanowire metamaterials embedded in air by selecting a smaller diameter (e.g. 15 nm) and a suitable q factor (e.g. 2 or 2.5).