Tuesday, November 25, 2014

Enabling The Next Generation Of Terahertz Devices

By Chuck Seegert, Ph.D.
A newly developed, single-component terahertz source was recently developed by researchers at Northwestern University. The device covers the full spectrum of terahertz radiation, comes in a small package, and is capable of functioning at room temperature. The device may enable new medical diagnostics and improve security measures at airports.
Many materials respond to terahertz radiation exposure by emitting characteristic spectroscopic signatures that can be used to identify them. Chemicals, biological specimens, drugs, and explosives are just a few of these materials. Like traditional X-rays, terahertz radiation can pass through tissue to form images. Unlike X-rays, however, this radiation doesn’t ionize the tissue and has a lower health risk.
Unfortunately, the generation of terahertz radiation has historically required equipment that is large and unwieldy, which doesn’t lend it to broad application in the field.
A recent advance from Northwestern University (NWU) researchers could now make terahertz radiation sources widely available, according to a recent press release from NWU. The detector could enable remote sensing in a number of settings, including airports, where identifying chemicals like explosives is critical. The technology would be particularly well suited for uses like this, since it could be deployed from a safe distance.
"A single-component solution capable of room temperature and widely tunable operation is highly desirable to enable next generation terahertz systems," said Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science at Northwestern University's McCormick School of Engineering and Applied Science, according to the press release.
Razeghi and her team have developed such a system, according to a recent study published by the team in Applied Physics Letters. The new single-component device is capable of producing a tunable frequency range from 2.6 to 4.2 terahertz at room temperature using pulsed lasers. The lasers used were mid-infrared quantum cascade lasers, and the radiation source could achieve terahertz power up to 0.1 mW. This range is much larger than ever achieved previously when electrical tuning is used.
Terahertz radiation exists between traditional electromagnetic waves, like those used in radios and microwaves, and photonic waves, like ultraviolet and infrared, according to a recent story fromPhotonics Online. Because of this, it may be a candidate for extending certain communication wavebands.

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