High Numerical Aperture Metalens for the Deep Ultraviolet

Deep-ultraviolet (DUV) light plays a pivotal role in advanced applications such as nanofabrication, biomedical imaging, and emerging photonic devices development. However, the lack of compact, high-performance optical components in this spectral range has hindered progress. Here, we demonstrate an aluminum nitride (AlN) metalens experimentally with a record high numerical aperture (HNA) from 0.9 to 0.7, operating at a DUV wavelength of 266 nm. Besides the optical measurement of the HNA metalens achieving a diffraction-limited focusing, we show that lithographic direct writing is not only employing the HNA metalens for nanofabrication but a universal and practical way to characterize the HNA DUV metalens especially considering the difficulties to build up a wideband HNA optical characterization system in this wavelength range. For applications, the HNA AlN metalens has been integrated in a confocal PL system and enables compact nanoscale spectroscopic imaging. This breakthrough establishes AlN metalenses as a transformative platform and practical solution for high-resolution DUV applications, bridging the gap between scalable metaoptics and next-generation photonic technologies in the deep-ultraviolet regime.