Gizmorama - May 30, 2016

Good Morning,

Infrared technology is going to get much more affordable thanks to a semiconductor that's capable of a nearly 99 percent light absorption rate. Trust me, prices are going to drop.

Learn about this and more interesting stories from the scientific community in today's issue.

Until Next Time,
Erin

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*-- Optics breakthrough could improve infrared technology --*
SYDNEY - New research out of Australia promises to dramatically reduce the price of infrared technologies like night vision goggles.

Scientists at the University of Sydney recently demonstrated a semiconductor capable of a nearly 99 percent light absorption rate. The semiconductor is just a few hundred atoms thick and could power a range of infrared devices.

The semiconductors currently used in night and fog vision technologies absorb light at a rate of just 7.7 percent, which means a larger amount of the material is necessary to power infrared vision.

"Conventional absorbers add bulk and cost to the infrared detector as well as the need for continuous power to keep the temperature down," Martijn de Sterke, a physics professor at Sydney, said in a news release. "The ultrathin absorbers can reduce these drawbacks."

"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," de Sterke added.

The semiconductor doesn't rely on any special material, and the engraving technique could be used to boost the absorption of older infrared semiconductors.

"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," explained lead researcher Björn Sturmberg.

There are already thin light-absorbing films, but making and using them is time-consuming and expensive. They either involve complex production processes or the use of nanostructures, meta-materials and other exotic materials.

"There are major efficiency and sensitivity gains to be obtained from making photo-detectors with less material," Sturmberg said.

The new research was detailed in the journal Optica.



* Terahertz spectroscopy could power bomb-detection technology *
BOSTON - Researchers at MIT and Princeton have built a new laser-powered terahertz spectroscopy system capable of detecting chemicals used in explosives.

Terahertz spectroscopy is the measurement of electromagnetic radiation between the frequencies of microwaves and infrared. Scientists have long realized the radiation's potential for bomb detection, but traditional terahertz spectroscopy systems are bulky and use lots of power. They also take a long time to analyze sample materials.

The new system uses a computer chip-size quantum cascade laser, and can detect terahertz signatures in just 100 microseconds.

The device produces a laser-powered frequency comb -- a spectrum made up of a series of equally spaced frequencies. The variety of frequencies allows the device to create a unique terahertz-absorption profile in just a few measurements.

The frequency comb is created by bouncing a laser back and forth through a gain medium composed of several hundred alternating layers of gallium arsenide and aluminum gallium arsenide. The layers are calibrated to propel the laser with just the right amount of energy to break through the gain medium.

Scientists tested their system by measuring the emissions frequency of an etalon, a double-mirrored wafer of gallium arsenide. Researchers were able to theoretically calculate the wafer's transmission spectrum prior to their experiment.

Their calculations and the experimental results matched up neatly, proving their spectroscopy system reliable.

Cascade lasers must be cooled to very low temperatures, a task that often requires rather bulky refrigeration systems. But because the quantum cascade laser frequency comb is so small, and because the laser uses very little energy, the new spectroscopy device doesn't need a big cooling system.

"We used to consume 10 watts, but my laser turns on only 1 percent of the time, which significantly reduces the refrigeration constraints," Yang Yang, a graduate student in electrical engineering and computer science at MIT, explained in a news release. "So we can use compact-sized cooling."

Yang is the first author of a new paper on the system, published this week in the journal Optica.

"With this work, we answer the question, 'What is the real application of quantum-cascade laser frequency combs?'" said Yang. "Terahertz is such a unique region that spectroscopy is probably the best application. And QCL-based frequency combs are a great candidate for spectroscopy."

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