Ultraviolet (UV) light is widely used in nanofabrication and biomedical fields. However, in order to shape the wavefront of the UV beam, UV light needs to travel a relatively long distance in optical media that usually have strong UV absorptions. Thus the traditional UV lens is inefficient, costly, and easily aging under the radiation. Hopefully, dielectric metalenses represent a promising alternative. We design and numerically study a polarization-insensitive and achromatic metalens at UV spectra from 234 to 274 nm. The metalens consists of 1519 AlN nanopillars and its focal length is about 4.7 μm, with a <4.6 % alternation over the entire operating bandwidth, whereas the alternation of a chromatic metalens is 24.3%. More importantly, the focal length remains nearly the same (<0.02 % alternation) for not only linearly polarized light with different polarization angles but also for the left-handed and right-handed circularly polarized light as well. In addition, the designed metalens still has an excellent convergence ability even at 10-deg oblique incidence. This polarized-insensitive and achromatic metalens will greatly promote the development of UV photonic devices and UV nanophotonics.
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