T-Rays Advance Toward Airport Screening

T-Rays Advance Toward Airport Screening

By Neil Savage at Technology Review Tuesday, February 20, 2007

A new laser design helps create usable terahertz radiation, which penetrates common materials but doesn't harm tissue.

Researchers around the world are trying to tap a barely used portion of the electromagnetic spectrum--terahertz radiation--to scan airline passengers for explosives and illegal drugs. The rays are particularly attractive: they can see through clothing, paper, leather, plastic, wood, and ceramics. They don't penetrate as well as x-rays, but they also don't damage living tissue. And they can read spectroscopic signatures, detecting the difference between, say, hair gel and an explosive.

While some commercial systems are already available for limited applications--one Japanese device scans mail for contraband drugs--a machine to scan airline passengers has been slow to evolve, mainly due to the difficulty of creating the terahertz radiation. The ideal scanner would send out a beam of t-rays at passing objects or at people a few meters away, then measure the rays reflected off the subjects and check them against a database of spectroscopic signatures. But most existing sources of t-rays only provide weak beams, which make detection slower and harder.


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