Ultra-Fast Light-Shaping Technology Could Be 'Game-Changer' For Future Imaging

Scientists have developed a new type of ‘virtual’ metasurface – capable of controlling light in ways traditional lenses and optics can’t – which they say is superior to the current approach which relies on ultra-thin engineered materials.

The Nottingham Trent University team says the work will help to fully optimise metasurface potential for a range of real-world applications and paves the way to a move from physical to virtual platforms in nanotechnology.

Metasurfaces are many times thinner than a human hair and can bend and focus light, change its colour and steer it in different directions, meaning they can replace bulky optical elements in small devices such as lenses, mirrors and filters.

While they are powerful however, the materials and dimensions of physical metasurfaces are fixed — once built, they can’t change their shape, which can limit how useful they are in real‑world technologies.

Now a team at Nottingham Trent University has led a study – published in the journal Advanced Photonics Nexus– demonstrating the potential for virtual metasurfaces, which use emulated two-dimensional optical patterns on a flat surface rather than tiny physical particles.

The process uses a device called a spatial light modulator, which can control light pixel by pixel to change its shape and function faster than the blink of an eye.

Because the patterns are programmable and can change instantly, the metasurface can perform many different functions within the same device. This could include mixing colours, turning invisible infrared images into visible, or acting like a lens to adjust focus.

The researchers argue that making the material ‘tuneable’ by using such synthesised metasurfaces is what is required to move metasurfaces out of laboratories and onto production lines into new technologies.

While the approach requires additional research and development, the team says that the approach could benefit a range of technologies, spanning imaging and microscopy, quantum photonics, sensing, beam steering, semiconductor manufacturing, telecommunications and holography.

In the new study, the researchers demonstrate the technology’s potential by using the approach to turn invisible infrared signals into visible pictures and adjusting the images’ focal lengths on demand. Conventional lenses and mirrors are unable to perform these two functions concurrently.

Working with researchers at the University of Brescia in Italy and Nankai University in China they were also able to generate the image at arbitrary focal lengths.

Traditional infrared cameras rely on expensive semiconductor sensors and separate optics but a programmable light pattern meant it was possible to convert infrared light into visible wavelengths that a standard camera could capture.

“Over the last decade or so, metasurfaces have been introduced as an alternative to larger optical elements and have been the backbone of the photonics revolution of the 21st Century,” said Mohsen Rahmani, Professor in Nanotechnology, Optics and Photonics in Nottingham Trent University’s School of Science and Technology.

He said: “Despite this, their tunability has been significantly limited, creating a bottleneck in laboratories and restricting their full potential. This new category of emulated, virtual metasurfaces can be the game-changer. Perhaps the best analogy is the transition from universe to metaverse – the 3D digital world where lifelike spaces exist but are not real.

“Our virtual metasurfaces can be dynamically reshaped in every 20 milliseconds, offering a completely distinct function, each time, within small gadgets and devices.”

Nottingham Trent University Associate Professor Lei Xu said: “Our virtual metasurfaces act like an imaginary toolbox containing every optical component. Employing AI to program virtual metasurfaces enables us to offer multimodal functions and enormous potential for real-life applications.”

Nottingham Trent University Research Fellow Dr Ze Zheng, the first author of this study, added: “Replacing physical metasurfaces with virtual metasurfaces can be viewed as a transition from analogue optical components towards more flexible digital platforms. This approach enables compact optical systems with enhanced programmability, multifunctionality, and reduced fabrication constraints, offering a promising route towards next-generation microscopes, cameras and imaging devices.”

The team, based in NTU's Advanced Optics and Photonics (AOP) Laboratories, were supported by the UK Research and Innovation Future Leaders Fellowship and the European Research Council Consolidator Grant.