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New Detection System Turns THz Light into Ultrasound Waves

Posted May 23, 2014

Terahertz (THz) light frequencies that have long eluded detectors can now be harnessed efficiently thanks to a new device developed at the University of Michigan.

The new approach solves the problem of detecting the so-called T-rays by transforming them into ultrasound waves that are relatively easy to spot. The photoacoustic transducer uses polydimethylsiloxane (PDMS) that expands after the THz light is absorbed by nanotubes and turned into heat.

PDMS creates an outgoing pressure wave by expanding, producing sound that is 1,000 times higher than what human ears can hear. This ultrasound wave is then captured by a microring resonator – microscopic plastic ring.

The newly developed system is superior to other heat-based THz detection devices because it doesn’t need a continuous stream of T-rays to work, but responds to the energy of individual THz light pulses, says lead researcher Jay Guo. Most existing THz detection techniques rely on bulky optics, or need cryogenic cooling, because otherwise they suffer from long integration times.

The new system will enable real-time THz imaging in many areas because its response speed is a fraction of a millionth of a second, explains Guo, a professor of electrical engineering and computer science, mechanical engineering, and macromolecular science and engineering at the University of Michigan.

THz light detectors could be used for airport security, because they would allow guards to detect chemical and other weapons. They could also help doctors do less damage to healthy areas when imaging body tissues. THz light scanning also opens up new possibilities for astronomers who study exoplanets.

Source: The Optical Society

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