|
With signatures of high photon energy and short wavelength, ultraviolet (UV) light enables numerous applications such as high-resolution imaging, photolithography and sensing. In order to manipulate UV light, bulky optics are usually required and thereby do not meet the fast-growing requirements of integration in compact systems. Recently, metasurfaces, with subwavelength or wavelength thicknesses, have shown unprecedented control of light, enabling substantial miniaturization of photonic devices from Terahertz to visible regions. However, material limitations and fabrication challenges have hampered the realization of such functionalities at shorter wavelengths. Herein, we theoretically and experimentally demonstrate that metasurfaces, made of highly scattering silicon (Si) antennas, can be designed and fabricated to manipulate broadband UV light. The metasurface thickness is only one-tenth of the working wavelength, resulting in very small height-to-width aspect ratio (~ 1). Peak conversion efficiency reaches 15% and diffraction efficiency is up to 30%, which are comparable to plasmonic metasurface performances in infrared (IR). A double bar structure is proposed to further improve the metasurface’s diffraction efficiency to close to 100% in transmission mode over a broad UV band. Moreover, for the first time, we show photolithography enabled by metasurface-generated UV holograms. We attribute such performance enhancement to the high scattering cross-sections of Si antennas in the UV range, which is adequately modeled via a circuit. Our new platform will deepen our understanding of light-matter interactions and introduce even more material options to broadband metaphotonic applications, including those in integrated photonics and holographic lithography technologies.
|
