A polarization-Insensitive Broadband Achromatic Metalens with High Efficiency in Ultraviolet-C band

Abstract: A metalens is composed of an array of artificially designed meta-atoms which can manipulate the phase, polarization and amplitude of light making it an excellent component for wavefront modulation. In this study, we design an transmittive achromatic metalens (NA equals to 0.05) composed of sapphire substrate and cross-shape silica meta-atom array operating across the entire ultraviolet C (UVC) band (200 to 280 nm) for all incident polarization through numerical simulation. It is shown that the device achieves an average focusing efficiency of 75% with a focal shift of less than 10% across the bandwidth and successfully demonstrates that is polarization-free. The device is expected to perform effectively in ultraviolet imaging and hold great potential for space-based astronomical observations.