High-Efficiency Optical Sparse Aperture Metalens Based on GaN Nanobrick Array

A flat and compact metasurface-based optical metalens with superior performance can be widely used on focusing and imaging. However, the realization of large-aperture metalens, which are composed of billions of nanoscale building blocks, poses significant challenges to both process technology and manufacturing cost. Herein, we develop an unconventional optical sparse-aperture (UOSA) metalens with a wiener filtering algorithm to obtain a high-quality image. The proposed UOSA metalens consist of three identical and concentric annular sectors sub-aperture metalens based on GaN nanobrick array, which can effectively focus the unpolarized visible light into the same point UOSA metalens. An effective aperture of 0.72 mm with lower cost is realized by utilizing less than 1/2 processing area. The experimental image results show that this all-dielectric UOSA metalens with a diffraction-limited resolution of 10.97 μm under 632.8 nm illumination is consistent with the simulation results. Furthermore, relatively high focusing efficiencies (> 50%) can also be achieved under the incident light with any polarization state. Our approach with less area process, time-saving, cost-effective, high efficiency, and large-aperture characteristics offer a vast application potential in the fields of integrated optical systems, near-eye imaging devices, and wearable optics.