Ultraviolet wavefront manipulation using topological insulator metasurfaces based on geometric phase

Metasurfaces, planar arrays of subwavelength optical phase shifters, show unprecedented superiority to convention bulk optical elements in many applications. Until now, most of metasurfaces work at frequencies from the microwave to the visible; material challenges (lack of media supporting resonant responses at higher frequencies) have hampered the realization of controlling light at shorter wavelengths. However, for applications such as high-resolution imaging and high sensitive sensing, they require much higher photon energy to meet the requirement of higher resolution. Herein, using plasmonic effect of topological insulator (Bi1.5Sb0.5Te1.8Se1.2, BSTS), we numerically demonstrate that the metasurfaces, composed of BSTS spheroidal nanostructures, operate in the ultraviolet range. Some representative wavefront shaping functions, including anomalous refraction, lensing and optical vortices, are realized by means of geometric phase scheme. This research may inspire more interest in the development of ultraviolet metasurface-based nano-photonic devices with diverse functions such as holographic lithography, subwavelength resolution imaging and quantum information processing.