Infra-red devices are used for improved vision through fog and for night vision and for observations not possible with visible light; high-quality detectors cost approximately $100,000 (including the device at the University of Sydney) some require cooling to -200°C.
Now, research spearheaded by researchers at the University of Sydney has demonstrated a dramatic increase in the absorption efficiency of light in a layer of semiconductor that is only a few hundred atoms thick - to almost 99 percent light absorption from the current inefficient 7.7 percent.
When light falls on a very thin, uniform layer almost all of it is reflected (right-hand arrows). By etching thin grooves in the film, the light is directed sideways and almost all of it is absorbed (left-hand arrows) even though the amount of material is very small. Insets show electron micrographs of the structuring. The absorbing layer is only 0.041 μm thick. CREDIT Dr Thomas P. White, Australian National University.
Optica Journal - Total absorption of visible light in ultrathin weakly absorbing semiconductor gratings
DARPA has a few programs to revolutionizing the cost of night vision
Defense Department scientists are working on a new, digital night vision and thermal device that’s smaller and lighter than the Army’s latest Enhanced Night Vision Goggle.
The analog night vision goggles (NVG) used by our troops to identify adversaries are limited to a single band of light. As NVGs also become available to adversaries as a commercial off-the-shelf product, the advantage in low- and no-light operation conditions is diminished. Current multi-band cameras, which may be used in a variety of environmental conditions, are too large and expensive for individual warfighters to carry.
DARPA’s PIXNET program aims to develop a low size, weight and power (SWaP); inexpensive; Soldier-portable digital infrared (IR) camera that will render real-time single and multiple-band imagery in both the thermal and reflective bands. The camera sought by DARPA would provide single band and multiple band fused imagery on demand, and afford troops with an enhanced situational understanding. A camera with these features would eliminate limitations posed by current assets to identify targets in multiple conditions: low-light, no-light, cluttered environment, etc.
PIXNET seeks significant reductions in SWaP, as well as low-cost manufacturing of IR sensors and coolers that may enable portability and wide deployment to all warfighters. The emphasis on a small form-factor naturally enables new applications, such as surveillance with small UAVs, rifle sights with multiple bands, and handheld surveillance systems.
PIXNET is a helmet-mounted camera that digitizes infrared capabilities. That saves a ton of weight; while an Enhanced Night Vision Goggle weighs around two pounds, the PIXNET camera weighs a fraction of a pound. It also would offer more settings, and be set up with a transmitter that could someday connect its signal to any of a series of devices, from a goggle to Family of Weapon Sights to a broader information technology platform like Nett Warrior.
The Low Cost Thermal Imager - Manufacturing (LCTI-M) program seeks to enable widespread use of infrared imaging technology by individual warfighters and insertion in small systems. The general use of infrared technology, at the individual warfighter level, may open possibilities for the implementation of new tactical procedures where a common view of the battlefield is essential for success. Infrared imaging has the capability to image through obscurants, providing valuable information even in environments with severely degraded visibility. Low cost infrared cameras will empower each warfighter with this essential capability. In addition, these cameras will enable the capture and transmission of electronic images for intelligence analysis and other critical situations.
The PIXNET camera is designed to provide small combat units with a helmet-mounted shortwave and longwave infrared blended imager with wireless networking capability. Photo: Matthew Cox, Military.com.
More on the Sydney night vision technology
Co-author from the University of Sydney's School of Physics, Professor Martijn de Sterke, said the team discovered perfect thin film light absorbers could be created simply by etching grooves into them.
"Conventional absorbers add bulk and cost to the infrared detector as well as the need for continuous power to keep the temperature down. The ultrathin absorbers can reduce these drawbacks," Professor de Sterke said.
"By etching thin grooves in the film, the light is directed sideways and almost all of it is absorbed, despite the small amount of material - the absorbing layer is less than 1/2000th the thickness of a human hair," he said.
Co-lead author Dr Björn Sturmberg, who carried out the research as a PhD student at the University of Sydney with the support of the Australian Renewable Energy Agency, said the findings did not rely upon a particular material but could be applied to many naturally occurring weak absorbers.
"There are many applications that could greatly benefit from perfectly absorbing ultra-thin films, ranging from defence and autonomous farming robots to medical tools and consumer electronics," Dr Sturmberg said.
The Director of Australia's National Computational Infrastructure (NCI) and co-author, of the paper, Professor Lindsay Botten, said the structures were much simpler to design and fabricate than using existing thin film light absorbers, which required either complex nanostructures, meta-materials and exotic materials or difficult-to-create combinations of metals and non-metals.
"There are major efficiency and sensitivity gains to be obtained from making photo-detectors with less material," he said.
SOURCES- University of Sydney, Optica Journal, Eurekalert, DARPA, Armytimes