# Dual-Wavelength Metalens Design for Compact LWIR and MWIR Imaging Systems

## TL;DR

This paper introduces a compact dual-wavelength metalens for infrared imaging that can focus both long-wave and mid-wave infrared light, enabling smaller and lighter thermal imaging systems.

## Contribution

The paper presents a novel inverse design strategy for dual-wavelength infrared metalenses with minimal focal length variation.

## Key findings

- The metalens focuses LWIR and MWIR radiation at 9.5 μm and 4.75 μm with 1% focal length variation.
- The system achieves dual-wavelength thermal imaging in a compact 26 × 26 × 18 mm3 form factor and 19 g weight.
- The design strategy is scalable and enables integrated, multifunctional infrared imaging lenses.

## Abstract

Multispectral infrared imaging systems that simultaneously operate in the long-wave infrared (LWIR) and mid-wave infrared (MWIR) bands offer significant advantages for target detection and recognition. However, conventional infrared optical systems rely on bulky multi-element lens assemblies to accommodate incident wavelengths of LWIR and MWIR bands, making it challenging for compact thermal optics design. Here, we propose and experimentally demonstrate an inverse designed infrared metalens capable of simultaneously focusing LWIR and MWIR radiation at wavelengths of 9.5 μm and 4.75 μm with a focal length variation of 1%. In the experiment, the proposed metalens with detector enables a dual-wavelength thermal imaging with a compact size (26 × 26 × 18 mm3) and a light weight (19 g). This work establishes a robust and scalable inverse design strategy for dual-wavelength infrared metalenses and provides a promising route toward compact, integrated, and multifunctional infrared imaging lens.