TECHNOLOGY FOR CHANGE

Better Detection of Hidden Explosives, Illegal Drugs

Rebecca Kutzer-Rice | Date: 07-21-10 | Comments

Researchers at the Rensselaer Polytechnic Institute are refining terahertz wave technology for use in an all-optical system for detection of hidden explosive devices and other contraband in airports and on battlefields.

Terrorist attacks like the attempted Christmas Eve bombing on a Northwest Airlines flight have led to an increased interest in bomb detection. Researchers at the Rensselaer Polytechnic Institute (RPI) are now using remote wave sensing to detect hidden explosives, chemical/biological agents, and other contraband from a distance of 20 meters.

The new system uses terahertz (THz) radiation, which lies at the far end of the infrared band of the electromagnetic spectrum, just before the microwave band. The unique properties of THz waves allow for better detection than traditional methods, such as X-rays. THz waves can, for example, pass through all substances except water and metal�from clothing to wood to plastic.

Substances like explosives emit specific THz �fingerprints.� The new system uses lasers to detect these waves and compare them to a directory of substances�allowing for instant identification.

The new system uses lasers to detect the terahertz radiation that all substances emit. Possible applications include detecting bombs and drugs in airports and locating explosives on battlefields (source: Rensselaer Polytechnic Institute/Daria Robbins).

Xi-Cheng Zhang, Director of the Center for THz Research at RPI, explains the technology in the university�s press release: �We have shown that you can focus an 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.�

Unlike other detection systems, such as X-rays, THz waves pose little to no health threat. Because the radiation cannot penetrate water, however, it cannot be used to detect substances hidden in the body.

Much of the research has been funded by the U.S. Departments of Homeland Security and Defense, which are eager for better explosives detection in airports and on battlefields.

�I think I can predict that, within a few years, the THz science and technology will become more available and ready for industrial and defense-related use,� Zhang states.

The research is detailed in an upcoming paper in Nature Photonics. Co-authors include Rensselaer�s Jingle Liu, Research Associate Professor Jianming Dai, and Professor See-Leang Chin of Quebec�s University of Laval.