Remote sensor detects any substance

A new remote wave sensing technology can see through clothing and packaging to detect explosives, biological agents and drugs from a distance of 20 meters.

The new all-optical system uses terahertz (THz) wave technology, which detects the unique THz ‘fingerprints’ of any hidden materials.

“The potential of THz wave remote sensing has been recognized for years, but practical application has been blocked by the fact that ambient moisture interferes with wave transmission,” said Xi-Cheng Zhang, director of the Center for THz Research at Rensselaer Polytechnic Institute.

The ‘all-optical’ technique uses laser-induced fluorescence, essentially focusing two laser beams together to remotely create a plasma that interacts with a generated THz wave.

The plasma fluorescence created is instantly compared with material spectrum in the THz ‘library’, allowing the immediate identification of a target material.

Because THz radiation transmits through almost anything that isn’t metal or liquid, the waves can ‘see’ through most materials that might be used to conceal explosives or other dangerous materials.

Unlike X-rays, THz radiation poses little or no health threat. However, the technique can’t detect materials that might be concealed in body cavities.

The technology is portable, and eventually could be used to check out backpacks or luggage abandoned in an airport for explosives, other dangerous materials, or for illegal drugs. On battlefields, it could detect where explosives are hidden.

Other uses could include monitoring chemical spills, where remote sensing could identify the composition of the toxic mix without endangering people.

Homeland Security and the Defense Department funded much of the research.