Ultraviolet lenses are core components of surveillance cameras, lithography machines and UV microscopes. Traditional refractive UV lenses are bulky, expensive and easy to aging, which hinders their applications in miniaturized and integrated photonic devices. In this paper, we proposed a polarization independent, broadband achromatic metalens that consists of arrays of silicon nitride nanopillars on a flat substrate. In order to simultaneously fulfill the target phases in a wide spectrum range, the phase library is extended to 0-8$\pi$ by using tall nanopillars that support high order resonances. The designed metalens has a stable focus across the entire operating wavelength range from 300 nm to 400 nm and the average focusing efficiency is as high as 50%. This polarization independent achromatic metalens can be potentially applied in compact UV cameras, UV microscopes and lithography machines.

紫外镜头是监控摄像机、光刻机和紫外显微镜的核心部件。传统的折射紫外透镜体积大、价格昂贵且容易老化，这阻碍了它们在小型化和集成光子器件中的应用。在本文中，我们提出了一种偏振无关的宽带消色差元透镜，它由平面基板上的氮化硅纳米柱阵列组成。为了同时满足宽光谱范围内的目标相位，相位库扩展到 0-8$\pi$通过使用支持高阶共振的高纳米柱。设计的超透镜在 300 nm 到 400 nm 的整个工作波长范围内具有稳定的聚焦，平均聚焦效率高达 50%。这种与偏振无关的消色差元透镜有可能应用于紧凑型紫外线相机、紫外线显微镜和光刻机。