Multilayer focal plane metalens based on all-dielectric materials in the ultraviolet band

Metalens can expand optical imaging capabilities due to the ability of metasurfaces to manipulate light propagation. Multi-focal metalens have been widely used in multi-imaging systems, detectors, and laser printing. This study presents the design of a UV metalens composed of alumina nanopillars. We investigate the focusing properties of representative UVA (343 nm) at multiple focal points on the in-plane axis, off-axis, and within a single plane. In addition, we extend the focusing ability of the metalens with multiple focal planes. We design the metalens with multiple imaging capabilities and produce focuses with different shapes in four focal planes. Simulation results show that the focal points of the planes have different shapes, the location of the maximum light intensity in the xz plane is in good agreement with our designed focal length, and the average focusing efficiency is greater than 60% in each plane. To evaluate the feasibility of planar spacing detection, we calculate the error-tolerant rate (Etr) of the device to be more than 90%. This work has important implications for the integrated miniaturization of UV photonic devices and the study of optical tomography.