An RGB-Achromatic Aplanatic Metalens

Optical metalenses offer a compact approach for the development of nanoscale optical devices with various imaging functionalities. Realizing high-quality images using metalenses with large numerical aperture (NA) requires eliminating unwanted optical aberrations. Existing strategies have largely focused only on correcting chromatic aberrations, and a metalens capable of simultaneously correcting chromatic and spherical aberrations has not yet been developed. Here, this issue is addresed by realizing an aplanatic phase profile for a red–green–blue (RGB) achromatic metalens, thereby demonstrating an RGB-achromatic aplanatic metalens. This device consists of crystalline silicon nanostructures and it enables RGB-achromatic aplanatic focusing with an NA of 0.635. The focal length of metalens remains unchanged at the three RGB wavelengths, whereas the associated focal spots are significantly smaller than those of an RGB-achromatic metalens with spherical aberrations. An enhanced RGB imaging resolution is demonstrated, offering exciting opportunities to power up various imaging and display applications using flat metalenses.