T-Rays Trapped for Better Security Scanners

A metamaterial structure that traps terahertz-frequency waves (T-rays) in microscopic holes could result in medical diagnostic and security scanners with higher sensitivity.

T-rays, used for airport body scanners and other security devices to see through packages and clothes, also can distinguish between malignant and healthy tissues in the detection of cancer.

Researchers at the University of Adelaide, in collaboration with scientists from RMIT University in Melbourne and Albert Ludwigs University in Freiburg, Germany, took an unconventional path to detect the waves, producing a structure of microscale cavities etched into the surface of silicon. T-rays hitting the structure were captured and compressed inside the cavities.

A concept design of the silicon-based metamaterial developed at the University of Adelaide. The structure that traps terahertz waves in microscopic holes could produce medical diagnostic and security scanners with higher sensitivity. Courtesy of Dr. Daniel White, ScienceFX.

“We needed to carefully select appropriate materials and processes to produce this device. We couldn’t construct the microcavities in our first choice of material, so we changed to silicon, which we had to adapt to make it slightly electrically conductive,” said RMIT team leader Dr. Sharath Sriram. “We then used established silicon microfabrication techniques to create the microcavities, exploiting the conductive properties.”

“By tailoring the silicon properties through the use of microstructures, it is possible to trap and confine the waves in a volume much smaller than the wavelength of the terahertz waves,” said Dr. Withawat Withayachumnankul, project leader and ARC postdoctoral fellow at the University of Adelaide’s School of Electrical and Electronic Engineering. “This significantly improves the efficiency of terahertz devices such as scanners and will have broad impact on biomedicine and homeland security, where better contrast means more accurate identification.”

The new structure could be added to conventional terahertz imaging devices to enhance their performance, the investigators say.

The research — supported by the Australian Research Council and in part by a Victoria Fellowship to Sriram — was published in Advanced Optical Materials (doi: 10.1002/adom.201300021).

For more information, visit: www.adelaide.edu.au