Scalable freeform optimization of wide-aperture 3D metalenses by zoned discrete axisymmetry

TL;DR

This paper presents a scalable framework for designing large 3D freeform metalenses using zoned discrete axisymmetry, enabling high-performance, large-scale meta-optics with nearly linear computational scaling.

Contribution

The authors introduce zoned discrete axisymmetry for metalens design, combining full-wave simulation and topology optimization to enable scalable, high-performance large-scale metalenses.

Findings

Designs outperform state-of-the-art metalenses.

Scalable approach with nearly linear computational cost.

Validated on millimeter and centimeter-scale lenses.

Abstract

We introduce a novel framework for design and optimization of 3D freeform metalenses that attains nearly linear scaling of computational cost with diameter, by breaking the lens into a sequence of radial "zones" with $n$-fold discrete axisymmetry, where $n$ increases with radius. This allows vastly more design freedom than imposing continuous axisymmetry, while avoiding the compromises of the locally periodic approximation (LPA) or scalar diffraction theory. Using a GPU-accelerated finite-difference time-domain (FDTD) solver in cylindrical coordinates, we perform full-wave simulation and topology optimization within each supra-wavelength zone. We validate our approach by designing millimeter and centimeter-scale, poly-achromatic, 3D freeform metalenses which outperform the state of the art. By demonstrating the scalability and resulting optical performance enabled by our "zoned discrete axisymmetry" (ZDA) and supra-wavelength domain decomposition, we highlight the potential of our framework to advance large-scale meta-optics and next-generation photonic technologies.