IR camera senses hot spots to aid firefighters, military pilots

Ashley N. Paddock, ashley.paddock@photonics.com

Firefighters and military pilots often use very cold, cumbersome infrared devices to detect hot spots and see through smoke, but a technology that uses gallium nitride (GaN) could eliminate the need for those conventional instruments.

Researchers at the University of Central Florida, led by professors David Hagan and Eric Van Stryland, have discovered that GaN – currently used to read Blu-ray DVDs – could offer an alternative to expensive liquid nitrogen, which boils at —200 °C.

Professor David Hagan, at right, and professor Eric Van Stryland, both of the University of Central Florida, have found that gallium nitride could replace liquid nitrogen to reduce the size of infrared detectors. Courtesy of the University of Central Florida.

Although much more research is needed, Hagan and Van Stryland believe that infrared sensors on military airplanes or lightweight cameras could be possible applications for their technology. Infrared detection and other thermal imaging systems are usually based on mercury cadmium telluride (MCT). Researchers have long wanted to see if GaN could detect infrared light and produce results similar to those achieved with MCT detectors.

To test the theory, the scientists used uncooled GaN detectors and employed two-photon absorption, using two photons of light at different wavelengths. They observed that GaN, as a semiconductor, is surprisingly sensitive to infrared. They used short bursts of light to conduct their initial experiments but soon plan to test the longer bursts that would be required to make the new technology practical, and they are looking to develop devices that can house it.

While the method is suitable for detection, they hope to expand into other applications such as all-optical switching, in which they could control one light beam with another. They have also envisioned two-photon gain and two-photon lasers.

The team’s research appeared online Aug. 7 in Nature Photonics (doi: 10.1038/nphoton.2011.168).