Significantly more effective scans conceivable for airport security or even in science
An inexpensive small-format terahertz camera from researchers at the Massachusetts Institute of Technology (https://www.mit.edu) (MIT), the University of Minnesota (https://twin-cities.umn.edu) and Samsung is enabling better security scans. Terahertz beams penetrate non-metallic materials. More effective scans at airports or industrial quality control as well as astrophysical observations as well as non-destructive characterizations of materials would be conceivable. The frequency range of terahertz waves is above 300 gigahertz.
Today’s terahertz devices are expensive, slow, bulky and require vacuum systems and extremely low temperatures. The new camera, which is still in the laboratory stage, can detect terahertz pulses quickly, with high sensitivity, and at room temperature and pressure. In addition, it simultaneously captures info about the orientation or “polarization” of the waves in real time, something existing devices cannot do. This data can be used to characterize materials with asymmetric molecules or to determine the surface topography of materials.
The new system uses particles called quantum dots that can emit visible light when stimulated by terahertz waves. This light is recorded by a device similar to the detector on a standard electronic camera. The photons of terahertz radiation have extremely low energy, according to Keith Nelson, a chemistry professor at MIT, which makes them difficult to detect. “This device converts that small photon energy into something visible that is easy to detect with a normal camera,” he says. In the team’s experiments, the device was able to detect terahertz pulses at low intensities that exceeded the capabilities of today’s large and expensive systems.
Terahertz difficult to generate
While the terahertz pulse detection problem appears to have been solved with the new work, the lack of good, inexpensive sources for terahertz beams remains. The usual approach is to generate them with multiple lasers and optical devices, an unsatisfactory solution for everyday practice. But there are hopeful approaches to producing sources using microelectronic techniques. “There is no question that this is coming,” Nelson concludes.