Metalenses are flat surfaces engineered by nanostructures to focus light. The surface has high aspect ratio nanostructures, made in high refractive index materials. This gives metalenses the benefit of being very thin compared to classical refractive optics. Metalenses can replace curved lenses and lens systems that are currently used in optical devices
Metalenses is a new field of optics. Currently, it is possible to design metalenses for single wavelengths with high efficiency. However, for broadband applications it is not as simple, since the metalens needs to correct for chromatic aberrations.
Like DOEs, it is possible to make metalens designs that correct for chromatic aberrations and even higher order aberrations and one of the interesting features of metalenses is that it is possible to control polarization.