New Glasses Coated with Lithium Enhance Vision in Low Light

Glasses coated with lithium compounds may one day help us see clearly in the dark.

For more than a decade, researchers have been searching for the best lightweight materials that can convert infrared light, invisible to the human eye, into visible light in order to provide an alternative to night-vision goggles, which are often heavy and cumbersome.

Until recently, the leading candidate was gallium arsenide. Laura Valencia Molina The researchers, from the Australian National University in Canberra, and their colleagues found that a film of lithium niobate coated with a lattice of silicon dioxide performed better.

“Through improved design and material properties, we have achieved a tenfold increase in the conversion rate from infrared to visible light compared to gallium arsenide films,” the team said. Maria del Rocio Camacho MoralesAt the Australian National University.

Through a series of experiments, the team demonstrated that the lithium niobate film could convert high-resolution images from infrared light with a wavelength of 1,550 nanometers to visible light with a wavelength of 550 nanometers, exceeding the capabilities of gallium arsenide.

Night vision goggles require infrared particles called photons to pass through a lens and be converted into electrons in a device called a photocathode. These electrons then pass through a phosphor screen to be converted into visible light photons. This entire process requires cryogenic cooling to prevent distortion of the image.

Molina says the lithium niobate film is hit by infrared light emitted by an object and illuminated with a laser at the same time. The film combines the infrared light with the laser light, which then up-converts the infrared light into visible light.

Camacho Morales says that one day, lattices of lithium niobate and silicon dioxide could be made into a film thinner than plastic wrap that could be coated over regular glasses to improve night vision.

While still in the research stage, the laser was positioned so that it could be easily shone onto the film along with infrared light emitted by the object, and the team is now experimenting with creating an array of nanolasers that can be positioned on top of the lithium niobate film.

The research is an important next step toward lightweight night-vision devices, and perhaps a film that can be attached to ordinary glasses, Camacho Morales said. It could also help drones navigate in the dark, he said, because current night-vision devices are too heavy to carry in some vehicles.