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Quantum cascade lasers "sniff-out" explosives

QCL application specialist Cascade Technologies has developed a way to detect explosives in airports rapidly.

The alleged plot to detonate liquid explosives on transatlantic flights from the UK - uncovered last week - was a firm reminder of the growing need for airport security.

However, according to scientists at Cascade Technologies in Stirling, Scotland, there might be a sensor available within two years that could "sniff-out" explosives as routinely as existing X-ray scanners check for illicit metal.

The device, which could be implemented as a portable hand-held unit, employs a III-V quantum cascade laser (QCL) to screen for potentially explosive substances.

Erwan Normand, the chief scientific officer at Cascade, claims that the device can "fingerprint" a material and check it against an on-board database in less than a second.

"Those fingerprints are unique, like an individual," he says. "They come from vibrations and rotations of the molecules. When we do a scan, the fingerprints recorded are compared to those on a database. If there is a match, it indicates we've pinpointed an explosive compound."

The device works by shining a QCL through a gaseous substance, and determining the absorption wavelengths through mid-infrared spectroscopy. Limiting the analysis to gases only, however, does not appear to be a problem.

"Every compound gives off gas," Normand continues. "We just look for traces of those gases. We can detect a single molecule out of a billion others."

Because they operate at room temperature, QCLs could be taken out of the lab and into the real world. "You could also implement the technology into existing X-ray screeners," claimed Normand. "Everything and everyone could be checked."

This means that the delays associated with hand-searching passengers' luggage could be a thing of the past.

The device makes significant headway over other methods of vapor trace detectors - or "sniffers" - because of its sensitivity, speed of operation, fingerprinting capability, size and cost. It is also less prone to giving false-positive results.

In addition, the technology could help with the detection of chemical warfare agents, toxic industrial chemicals and narcotics.

In a proof-of-concept two months ago, the team successfully fingerprinted two explosive compounds in just 10 milliseconds. They now want to obtain sufficient funding to continue the demonstration phase and expand the database.

"The platform is already there," says Normand. "But the whole process could be sped-up with some additional resources."

Jon Cartwright is a reporter for compoundsemiconductor.net and Compound Semiconductor magazine.

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