Image via WikipediaThe new, all-optical system, using terahertz (THz) wave technology, has great potential for homeland security and military uses because it can "see through" clothing and packaging materials and can identify immediately the unique THz "fingerprints" of any hidden materials.
Terahertz waves occupy a large segment of the electromagnetic spectrum between the infrared and microwave bands which can provide imaging and sensing technologies not available through conventional technologies such as x-ray and microwave.
"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," says Xi-Cheng Zhang, Ph.D., director of the Center for THz Research at Rensselaer.
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.
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.
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