A breakthrough in remote wave sensing by a team of Rensselaer Polytechnic Institute researchers uses unique terahertz (THz) “fingerprints” to identify hidden explosives, chemical, biological agents, and illegal drugs from a distance of 20 meters.

The new all-optical system has great potential for homeland security and military uses because it can “see through” clothing and packaging materials.

Dr. Zhang, the J. Erik Jonsson Professor of Science at Rensselaer, is lead author of a paper to be published next week in the journal Nature Photonics. Titled “Broadband terahertz wave remote sensing using coherent manipulation of fluorescence from asymmetrically ionized gases,” the paper describes the new system in detail.

Crossing laser beams generates “laser induced fluorescence” to identify materials

The “all optical” technique for remote THz sensing uses laser induced fluorescence, essentially focusing two laser beams together into the air to remotely create a plasma that interacts with a generated THz wave. The plasma fluorescence carries information from a target material to a detector, where it is instantly compared with material spectrum in the THz “library,” making possible immediate identification of a target material.

“We have shown that you can focus a 800 nm laser beam and a 400 nm laser beam together into the air to remotely create a plasma interacting with the THz wave, and use the plasma fluorescence to convey the information of the THz wave back to the local detector,” explains Dr. Zhang.

Though most of the research has been conducted in a laboratory setting, 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.

More info: Rensselaer Polytechnic Institute news