Multilayer dielectric metalens.

We propose and analyze a metalens whose meta-atoms (nanoscatterers) are integrated by a stack of quarter-wave dielectric layers. Each multilayer meta-atom is a nanopillar, which consists of alternating layers of high- and low-refractive-index materials. We show that the nanopillars of a multilayer metalens may have a smaller aspect ratio than the nanopillars of a standard metalens and have similar optical properties (focusing efficiency and chromaticity).