High-efficiency, large-area, topology-optimized metasurfaces

TLDR

Metasurfaces are ultrathin optical elements that promise lightweight, compact optical systems, yet their practical use requires maximizing efficiency, a goal that topology optimization can achieve but has been limited to microscale devices due to high computational demands. This work introduces a strategy for efficiently optimizing large‑area metasurfaces. The approach stitches individually optimized sections, reducing optimization complexity from high‑polynomial to linear. The authors designed and experimentally demonstrated large‑area, high‑NA silicon metasurface lenses with focusing efficiencies exceeding 90%, and show the method generalizes to multifunctional broadband diffractive devices for practical large‑area high‑performance metasurfaces.

Abstract

Metasurfaces are ultrathin optical elements that are highly promising for constructing lightweight and compact optical systems. For their practical implementation, it is imperative to maximize the metasurface efficiency. Topology optimization provides a pathway for pushing the limits of metasurface efficiency; however, topology optimization methods have been limited to the design of microscale devices due to the extensive computational resources that are required. We introduce a new strategy for optimizing large-area metasurfaces in a computationally efficient manner. By stitching together individually optimized sections of the metasurface, we can reduce the computational complexity of the optimization from high-polynomial to linear. As a proof of concept, we design and experimentally demonstrate large-area, high-numerical-aperture silicon metasurface lenses with focusing efficiencies exceeding 90%. These concepts can be generalized to the design of multifunctional, broadband diffractive optical devices and will enable the implementation of large-area, high-performance metasurfaces in practical optical systems.