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Recent years have witnessed the rapid development of flat optical elements (i.e., metasurfaces). With properly designed and arranged sub-wavelength structures over its plane, a metasurface is able to impart arbitrary, spatially variant amplitude, phase and polarization modulations on an incident electromagnetic wave. This highly customizable nature allows metasurface to simultaneously accomplish a variety of functions that have traditionally been fulfilled by a combination of different optics, such as gratings, lenses, beam splitters, and hologram plates, with a significantly reduced physical thickness compared to traditional optical elements. Researchers have demonstrated various high-performance metasurfaces operating in the infrared (IR) and visible regime. However, there has been a conspicuous lack of work in the ultraviolet (UV) region, which is a spectral range hosting important applications such as photolithography, DNA sequencing, sterilization, and medical imaging. Unfortunately, direct translation to the UV regime of implementation strategies for IR and visible-frequency metasurfaces will not work, so new constituent materials and designs need to be developed.
Here, we report on high-efficiency, all-dielectric metasurfaces operating in the UV regime. The metasurfaces utilize wide bandgap (> 5.5 eV) dielectric materials, enabling the devices to operate over a broad-band UV range. We demonstrate metasurfaces working at three UV wavelengths (364, 325 and 266 nm), including hologram, lens, and self-accelerating beam devices. To further show the versatility of our design, we demonstrate metasurfaces producing spin-multiplexed holograms and self-accelerating beams at 364 nm, with operational efficiencies larger than 50%. Our work opens the door for high-performance and multi-functional UV flat optical elements.
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