# Overlapping domains for topology optimization of large-area metasurfaces

## TL;DR

This paper presents an overlapping-domain method for large-area metasurface design, significantly improving accuracy and efficiency in creating high-quality metalenses with complex optical properties.

## Contribution

The authors develop a novel overlapping-domain approach combined with topology optimization, enabling more accurate and efficient design of large-area metasurfaces.

## Key findings

- Achieved ~10x better accuracy over local periodic approximation.
- Designed large-area, high-NA, broadband achromatic lenses with ~50% efficiency.
- Demonstrated significant improvement in metalens quality and performance.

## Abstract

We introduce an overlapping-domain approach to large-area metasurface design, in which each simulated domain consists of a unit cell and overlapping regions from the neighboring cells plus PML absorbers. We show that our approach generates greatly improved metalens quality compared to designs produced using a locally periodic approximation, thanks to $\sim 10\times$ better accuracy with similar computational cost. We use the new approach with topology optimization to design large-area ($200\lambda$) high-NA (0.71) multichrome and broadband achromatic lenses with high focusing efficiency ($\sim 50\%$), greatly improving upon previously reported works.