Terahertz Remote Sensors See Through Walls
New terahertz remote sensors can see objects through walls…
Advancements in terahertz remote sensing could lead to the development of devices that could see through walls, clothing and packaging to identify what objects may be laying on the other side.
Previous terahertz remote sensors could only work at distances of a few inches because terahertz waves are easily absorbed by moisture in the air.
Lead author of the new study Jingle Liu of Rensselaer Polytechnic Institute, said, “A lot of other researchers thought that terahertz remote sensing was mission impossible.”
Terahertz Remote Sensors
Liu’s team solved the problem by using lasers to create a reflection of the terahertz waves.
The team found that pointing two lasers with different frequencies at the target generated a plasma – excited or ionized air. This plasma emits a florescence that is scattered by the terahertz radiation of the material it hits and this ‘reflection’ of the florescence is detectable from remote distances.
Laser Frequencies Of New Terahertz Remote Sensors
The researchers have tested hundreds of different substances and created a library of terahertz spectra to compare to the signal from the target and instantly identify the material that was hit.
The researchers demonstrated that they could detect the signal from 67 feet away, the length of their laboratory space, but theoretically they could identify materials hundreds of feet or even miles away, Liu said.
Expert Abul Azad at Los Alamos National Laboratory said:
“Homeland security and military agencies have been struggling for years to get technology like this. I think the approach they have revealed is really, really unique.”
With Homeland Security and the Defense Department putting most of the funds for the research, the technology will likely see its first military application in detecting roadside bombs otherwise known as improvised explosive devices (IDE), which continue to be an ever present threat on the Middle East.
Terahertz detectors could also be used for airport security to detect illegal substances hidden in people’s clothes. The approach would be less invasive than x-rays, Liu said, because terahertz waves are much lower in energy. It would not reveal anything concealed inside the body, because the terahertz signals cannot go through water, or metal.
The study was published July 11 in Nature Photonics.
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