Large-area multiwavelength and polarization-insensitive metalenses via multilayer Huygens metasurfaces

TL;DR

This paper presents a novel multiwavelength, polarization-insensitive metalens design using multilayer Huygens' metasurfaces, enabling large-area, broadband focusing in the near-infrared with high efficiency and fabrication compatibility.

Contribution

Introduces a multilayer Huygens' metasurface approach for large-area, multiwavelength metalenses that are polarization-insensitive and compatible with scalable fabrication.

Findings

Achieves near-diffraction-limited focusing at 2000 and 2340 nm

Demonstrates high focusing efficiencies of 65% and 56%

Design is compatible with large-area nanofabrication techniques

Abstract

Metalenses, advanced nanostructured alternatives to conventional lenses, significantly enhance the compactness and functionality of optical systems. Despite progress in monochromatic applications, scaling metalenses to centimeter-sized apertures for broadband or multiwavelength use remains challenging due to limitations in achieving the necessary group delay (GD) with current materials. In this study, we introduce a novel multiwavelength, polarization-insensitive metalens design operating in the near-infrared (NIR). Our approach employs multiple Huygens' metasurface layers, each optimized to modulate a specific wavelength while maintaining high transmittance and minimal phase disturbance at other wavelengths. We demonstrate a metalens operating at 2000 and 2340 nm with a numerical aperture (NA) of 0.11. In simulation, the metalens achieves a normalized modulation transfer function (MTF) that is nearly exactly diffraction-limited. The absolute focusing efficiencies are 65% and 56%, corresponding to relative efficiencies of 76% and 65% compared to an ideal lens of the same dimensions. The meta-atoms are designed using an inverse shape-optimization method that ensures polarization insensitivity and high tolerance to layer misalignment. The proposed design is compatible with large-area nanofabrication techniques, allowing metasurface layers to be fabricated individually and assembled into the final device. This innovative approach is also generalizable to any arbitrary multiwavelength phase profile beyond that of simple lensing.