A breakthrough in tiny, color-rich optics
Researchers have unveiled a novel approach to making ultra-thin lenses that can simultaneously focus multiple wavelengths from unpolarised light, with potential workhorse applications in phones, drones, and other portable imaging devices. The key advance is a multi-layer, metamaterial-based metalens system that uses a stack of carefully engineered layers to control light across a broad color range.
The design, developed by Joshua Jordaan and colleagues at the Australian National University (ANU) and the ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), builds on a longstanding limitation of conventional metalenses: a single layer struggles to bend different wavelengths efficiently across a large diameter. By moving to several layers, the team unlocked a pathway to higher numerical apertures and larger imaging areas without sacrificing color fidelity or polarisation independence.
Why multi-layer metalenses matter
Metalenses are thin, nanostructured surfaces that can shape light with extraordinary precision. Yet achieving high performance across multiple wavelengths in a scalable way has been challenging. Jordaan explains that a single-layer metasurface has physical constraints that cap the product of aperture, bandwidth, and focusing strength. “To work at the wavelength range we needed, a single layer would either have a very small diameter, which would defeat the purpose of the design, or would have such a low numerical aperture that it wouldn’t focus light effectively,” he said.
The team therefore adopted a multi-layer approach, using an inverse design algorithm to optimize shapes across multiple metasurface layers. The algorithm searches a broad library of nano-elements—some resembling rounded squares, four-leaf clovers, and propeller shapes—to create resonances that enhance light control. By engineering both electric and magnetic dipole resonances (Huygens resonances), the layers collaborate to deliver desired phase shifts and focal properties for several wavelengths at once.
The result is a polarization-insensitive system that remains manufacturable with existing semiconductor nanofabrication platforms. Each layer has a relatively low aspect ratio, facilitating individual fabrication and relatively straightforward packaging. This makes the technology more scalable for industrial production and consumer devices alike.
From concept to potential devices
The multi-layer metalens can span a broad phase range—from zero to two pi—enabling the construction of a phase gradient map that achieves complex focusing patterns. Early demonstrations show the ability to route different colors to different locations, effectively creating a color router within a single compact optic. While the current work caps the number of wavelengths at around five due to structural resonant constraints, the improvement in light collection efficiency and color management marks a meaningful leap for portable imaging.
“Our design has a lot of nice features that make it applicable to practical devices,” says Jordaan. The practical implications are especially compelling for small airborne platforms and compact cameras where weight, size, and power are at a premium. The researchers envision drones or earth-observation platforms benefiting from calendar-light, high-quality imaging optics that can be produced at scale without the bulk of conventional multi-lens assemblies.
Implications for consumer tech and industry
For consumer electronics, the prospect of bold new optics that are lighter, cheaper, and more capable is particularly attractive. A stack of metamaterial lenses could reduce the need for bulky multi-element lenses while delivering better control over color separation and light gathering. In addition, the thinness and compatibility with semiconductor fabrication hint at reduced manufacturing costs and improved production yields—critical factors for mass-market devices such as smartphones and small drones.
The multi-layer metalens concept also promises enhancements for specialized applications, including high-resolution imaging in small satellites or compact terrestrial cameras, where the combination of lightweight optics and robustness to polarisation errors can translate into tangible performance gains.
The research team published their results in Optics Express, highlighting that the approach represents a meaningful step toward practical, scalable metasurfaces capable of multi-wavelength focusing. While the current design prioritizes five wavelengths, ongoing work aims to push both the spectral range and the angular performance to meet real-world imaging needs.
Looking ahead
With continued refinement, multi-layer, metamaterial-based metalenses could power the next generation of tiny, high-performance optics for drones, cameras, and mobile devices. By combining advanced inverse design with layers designed to resonate at key wavelengths, researchers are moving closer to affordable, lightweight optics that deliver crisp, color-accurate images in everyday tech.
