Hearing Light: New Technique Converts T-Rays into Sound Waves

Can you imagine hearing light? That's exactly what a new device does. The technology "listens" for light waves and could help open up the last frontier of the electromagnetic spectrum-the terahertz range.

So-called T-rays are light waves that are too long for human eyes to see. In theory, these light waves could potentially help airport security guards find chemical and other weapons and could even allow doctors to image body tissues with less damage to healthy areas. Yet because terahertz frequencies fall between the capabilities of the specialized tools presently used to detect light, scientists have been unable to find a way to harness them-until now.

The terahertz gap is actually a sliver between the microwave and infrared bands of the electromagnetic spectrum. The spectrum itself spans from the longest, low-energy radio waves that carry songs to our receivers to the high-energy gamma rays that are released when nuclear bombs exploded.  While the terahertz gap is "scientifically rich," today's detectors are bulky or need to be kept cold to work.

The new system could potentially help bridge the terahertz gap. The scientists created a special transducer that makes light-to-sound conversion possible, converting one form of energy into another. Essentially, the scientists use a detector to convert the T-ray light into sound. The sound that the detector makes is too high for human ears to hear-an ultrasound wave.

"We convert T-ray light into sound," said Jay Guo, one of the researchers, in a news release. "Our detector is sensitive, compact and works at room temperature, and we've made it using an unconventional approach."

While ultrasound detectors exist, the researchers created their own in the form of a microscopic plastic ring known as a microring resonator. They then connected their system to a computer and showed that they could use it to scan and produce an image of an aluminum cross.

The findings reveal a way to potentially harness T-rays. This could be huge for the future of scanning in both medical and security applications.

The findings are published in the journal Nature Photonics.