Overview: A new path to ultra-compact, color-rich optics
Researchers have unveiled a groundbreaking approach to creating multicolor lenses that are thinner than a hair and capable of focusing a broad range of wavelengths from unpolarised light. By using layers of metamaterials in a carefully engineered stack, the design overcomes key limitations of traditional metalenses and opens the door to affordable, tiny, and powerful optics for portable devices such as smartphones and drones.
How the multilayer metalens works
The innovation centers on stacking multiple metalens layers, each engineered to interact with different wavelengths. This multilayer strategy allows the device to focus multiple colors simultaneously while maintaining a large aperture. The concept was developed by a team led by Joshua Jordaan of the Research School of Physics at the Australian National University and the ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), in collaboration with researchers from Friedrich Schiller University Jena, as part of the Meta-ACTIVE program.
Single-layer metasurfaces hit physical limits: there is a cap on how much phase and delay can be imparted, which constrains the achievable numerical aperture and bandwidth. A multi-layer approach sidesteps these barriers by introducing a broader range of resonant interactions across layers. The team used an inverse design algorithm to explore a diverse library of metamaterial shapes and resonance modes, including both electric and magnetic (Huygens) resonances, to craft effective phase gradients for precise focusing.
Design details and manufacturing practicality
The metasurface elements are around 300 nanometers tall and 1000 nanometers wide, with phase shifts spanning zero to two pi. This enables complex phase gradient maps that realize arbitrary focusing patterns beyond a simple lens geometry. The algorithm’s output produced shapes ranging from rounded squares to more intricate forms like propellers, expanding the toolbox for optical engineers.
A key advantage of the multilayer concept is manufacturability: each layer features a low aspect ratio, can be fabricated separately, and then stacked. The design is polarization-insensitive and compatible with mature semiconductor nanofabrication platforms, making it scalable for industrial production. This combination of robustness and simplicity addresses one of the biggest hurdles to deploying metalenses in consumer devices.
What this means for devices like phones and drones
With this multilayer metalens approach, compact optics can collect more light, improve color handling, and deliver sharper images without the bulk of conventional lenses. While the current work focuses on a five-wavelength limit dictated by resonant structures, it already demonstrates practical benefits for portable imaging systems. In ideal scenarios, a smartphone or a small drone could carry lightweight, inexpensive optics that deliver high-quality, multicolor imaging—potentially transforming photography, videography, and sensing in consumer electronics.
Applications and future potential
The researchers highlight drones and Earth-observation satellites as prime candidates for these tiny, light lenses, where weight savings translate directly into energy efficiency and longer flight times. Beyond aerial imaging, the same multilayer metalens concepts could inform compact endoscopes, wearable cameras, and other portable sensors that demand minimal bulk without sacrificing color fidelity or light throughput.
Limitations remain, notably the practical cap of handling roughly five distinct wavelengths within a single stack. Researchers are optimistic that further refinements in material choice, layer count, and optimization could broaden the spectral range while preserving manufacturability and polarization insensitivity.
Conclusion: A scalable route to next-gen optics
The move from single-layer to multilayer metamaterial lenses offers a credible path toward real-world, pocket-sized optics for drones and smartphones. By combining polarization independence, a forgiving manufacturing process, and a pathway to scalable production, this breakthrough could redefine how imaging systems in everyday devices capture color, light, and detail.
