Infrared light's demand has consistently grown over the past years due to its wide variety of applications that could range from food quality control and remote sensing to night vision goggles. The technology has captured the popular imagination as seen in action movies and several video games, like Call of Duty.

However, it comes not without problems because commercial infrared cameras block visible light that disrupts normal vision, plus the gear is bulky and heavy and needs low temperatures for them to work.

Researchers from The Australian National University, Nottingham Trent University, and collaborators worldwide proposed using ultrathin nanocrystal layers to address these problems in current devices.

 Infrared Imaging Could Be An Everyday Reality Using Ultrathin Nanocrystal Layers
(Photo: Wikimedia Commons)
Comparison of an Osteospermum ecklonis flower photographed in visible light (left), ultraviolet light (middle), and infrared light (right).

Drawbacks o Commercial Infrared Cameras

Night vision goggles and infrared cameras detect infrared light emitted or reflected by objects in the form of heat. These devices are not only used in the military but as well as other law enforcement and emergency services. Security and surveillance industries, wildlife hunters, and camping enthusiasts also use this technology.

Rocio Camacho Morales, a post-doctoral fellow at Australian National University, published an article in The Conversation saying that commercial infrared detectors convert infrared (IR) light to an electric signal that is shown to the display screen.

However, these devices need low energy and frequency of IR light that makes them bulky and heavy. There was even a study about some security personnel reporting chronic neck injury because of the regular use of night vision goggles.

Another drawback to current commercial infrared detectors is that they block visible light, which disrupts normal vision. They tried solving it by sending infrared images to a display monitor, but this solution is not feasible when soldiers or users are on the move.

Some all-optical alternatives do not use electrical signals but directly convert lights into visible. However, they use nonlinear crystals, which are bulky and expensive.

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Using Ultrathin Nanocrystal Layers As Solution

In the study, entitled "Infrared upconversion imaging in nonlinear metasurfaces," published in the journal Advanced Photonics, researchers proposed a solution to the longstanding problems of using current infrared detectors. They used layers of ultrathin nanocrystals, called metasurfaces, that can be tweaked to manipulate the color or frequency of light that can pass through it.

The metasurfaces used in the study were fabricated and transferred into the transparent glass to form layers of nanocrystals on the glass surface, according to Science Codex.

In the experiment, the infrared image of a Siemens-star target illuminated the metasurfaces, and researchers saw that infrared images were converted to green visible images.

They tested it with various positions of the target and even removing the target from the path of the infrared beam to see the green light emitted by the metasurfaces. They found that it corresponds to various traverse positions of the target.

They saw images were formed into the visible light despite some parts of the infrared signal beam is converted by independent nanocrystals in the metasurfaces.

This new metasurface-based infrared imaging detector offers novel opportunities that are conventional infrared detectors can do. The findings of the experiment could be used to develop future compact night vision and sensor devices with a broader angle of view and multi-color infrared imaging at room temperature.

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