Imaging technology could see a quiet revolution as researchers unveil multilayer metalenses that can focus multiple colors simultaneously in a footprint thinner than a strand of hair. The layered metasurface approach, developed by researchers at the Australian National University (ANU) and the ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), uses stacked metamaterial layers to extend the range of wavelengths and the size through which light can be focused. The work, published in Optics Express, suggests a viable path toward portable, high-performance optics for drones and smartphones.

The breakthrough hinges on moving beyond the single-layer constraint that has long limited metalenses. A single layer can offer excellent miniaturization, but its performance across a broad color range, or across a wide numerical aperture, is inherently limited by the physics of group delay in metasurfaces. By stacking multiple metasurface layers and optimizing their shapes, the team achieved resonances in both electric and magnetic dipoles—Huygens resonances—that collectively shape the phase of incoming light. Importantly, the design remains polarization-insensitive, which means the metalenses perform similarly for light with different polarization states, a crucial attribute for real-world imaging where polarization varies with scene and weather. For defense planners, the message was unmistakable: lighter, more capable optics can expand mission envelopes and reduce risk in airborne operations.

In mid- and small-scale devices, such as consumer drones or handheld cameras, manufacturing flexibility matters. The researchers used an inverse design algorithm that searches a library of nano-structures, enabling a high degree of control while tolerating fabrication variations. The resulting library included unconventional shapes such as rounded squares, four-leaf clovers, and even propeller-like motifs. These shapes, roughly 300 nanometers tall and 1,000 nanometers wide, produce a complete phase range from 0 to two pi, enabling a phase gradient that can steer and shape focus across wavelengths.

Practically, a color router is imaginable: different wavelengths could be focused at different spots to create color separation or to fans out into a tailored focus pattern. That capability expands the toolbox for portable imaging, where weight, size, and power constraints demand optical elements that do more with less. The researchers note that the multiwavelength performance is currently best across about five wavelengths, a limit set by the need for resonant structures large enough for the longest wavelength without undesired diffraction at shorter ones. Nonetheless, even with this constraint, multilayer metalenses could dramatically improve light collection efficiency in compact cameras and lightweight drones.

What this breakthrough means for imaging

For defense planners and civil operators alike, the promise of multilayer metalenses is threefold: significant weight reduction for aerial platforms, simpler assembly through layer-by-layer fabrication, and meaningful cost savings from leveraging mature semiconductor processes. The shorter optical path and thinner form factor can translate into longer flight times and more compact payloads—critical advantages for small UAS missions in agriculture, disaster response, and infrastructure inspection. For consumers, the trend points toward smarter sensors in smartphones and portable cameras that can run at higher aperture or lower noise without bulky glass elements.

How multilayer metalenses work

• Stacked layers create coupled resonances that shape phase across multiple wavelengths.
• Inverse design identifies nano-structures to meet multiwavelength, polarization-insensitive goals.
• Shapes range from rounded squares to propellers, enabling a full 0-to-2π phase control.

Implications for drones and portable devices

In drones, lighter optical assemblies can boost endurance and payload flexibility. In portable cameras, the reduced bulk could enable new form factors or better low-light performance due to improved light gathering. The practical appeal is not just better optics; it is a streamlined supply chain that can leverage existing semiconductor fabrication infrastructure and scale to mass production. For imaging professionals, multilayer metalenses could become a differentiator in the competitive drone and smartphone ecosystems.

Limitations and next steps

While the multilayer approach breaks new ground, the current design focuses on a handful of wavelengths. Extending to a larger color spectrum will require further innovations in layer count, materials, and fabrication tolerances. The team emphasizes that continued advances in metasurface design, materials science, and lithography will be essential to bring these metalenses from lab benches to production lines. In the near term, expect incremental demonstrations in specialized imaging systems, followed by broader adoption as manufacturing ecosystems mature.

Conclusion

Multilayer metalenses represent a pragmatic path forward for ultra-compact, high-performance imaging. By stacking metasurface layers and exploiting Huygens resonances, researchers have opened a route to multiwavelength, polarization-insensitive lenses that can transform drone and smartphone cameras. For the industry, the signal is clear: the era of truly flat, lightweight, versatile optics is nearer than many imagined, and it could redefine how we capture the world from the air and in our pockets.