Inverse Design of High-NA Metalens for Maskless Lithography

TL;DR

This paper presents an inverse-designed axisymmetric metalens that enhances maskless lithography by achieving high transmission efficiency and experimental validation, potentially enabling low-cost, large-area nanofabrication.

Contribution

The work introduces a novel inverse design method for high-NA metalenses with experimental validation, surpassing traditional gradient index lens efficiency.

Findings

Achieved 85.50% transmission normalized focusing efficiency at 0.6 NA and 405nm wavelength.

Demonstrated fabrication-compatible inverse-designed metalens with superior efficiency.

Validated the metalens performance through electron beam lithography experiments.

Abstract

We demonstrate an axisymmetric inverse-designed metalens to improve the performance of zone-plate-array lithography (ZPAL), one of the maskless lithography approaches, that offer a new paradigm for nanoscale research and industry. First, we derive a computational upper bound for a unit-cell-based axisymmetric metalens. Then, we demonstrate a fabrication-compatible inverse-designed metalens with 85.50\% transmission normalized focusing efficiency at 0.6 numerical aperture at 405nm wavelength; a higher efficiency than a theoretical gradient index lens design (79.98\%). We also demonstrate experimental validation for our axisymmetric inverse-designed metalens via electron beam lithography. Metalens-based maskless lithography may open a new way of achieving low-cost, large-area nanofabrication.