High-space–bandwidth product characterization of metalenses by information fusion of multi-angle illumination

In the fields of biomedical and astronomical imaging, large numerical aperture (NA) and large aperture metalenses have demonstrated remarkable performance and extensive applications. However, characterizing the phase of these metalenses, which have small phase periods and large apertures, has been challenging due to the high space–bandwidth product (SBP) requirements. To characterize these metalenses, we present a high-SBP phase characterization technique based on information fusion of multi-angle illumination (IFMI), inspired by Fourier ptychographic microscopy. Our method offers comparable accuracy to interferometry without its susceptibility to vibration while also surpassing most computational imaging methods in accuracy and eliminating the need for mechanical movements. Our findings indicate that this technique not only breaks through the phase measurement bottleneck of the focusing metalens with a large NA of up to 0.59 but also actualizes the investigation to measure the phase of the focusing vortex metalens. By utilizing the measured phase, we further quantitatively explore the effect of fabrication errors on the typical optical performance of the focusing metalens and focusing vortex metalens. Additionally, to compensate for the corresponding optical system performance, a convenient and economic alignment strategy is conducted, significantly reducing the difficulty of redesigning and refabricating metalenses. We believe that these characterization results, based on our high-SBP characterization technique, can not only guide the development direction of the design method and fabrication process of metalenses but also provide a gold standard for its alignment processing, which will pave the way for the diversified applications of metalenses.