Scientists have made new miniature devices that could be developed into safe, high-resolution imaging technology that helps doctors to identify potentially deadly cancers and treat them early.

Millions of people around the world die from cancer every year.

The Australian National University (ANU) collaborated on the new devices with the University of Strathclyde and Oxford University in the UK.

One of the lead researchers Professor Lan Fu said the devices use terahertz radiation, which can penetrate through materials such as plastics, wood and skin. She said terahertz radiation, which falls between infrared and microwaves in the electromagnetic spectrum, does not damage living tissues like X-rays.

“These tiny devices are made from nanowires that are one hundred times thinner than a human hair, yet they could hold the key to some very powerful imaging and sensing technologies,” said Professor Fu from the ANU Research School of Physics.

“They could help create a new safe imaging technology with much higher resolution than current ultrasound devices used to detect small tumours that doctors can adopt for regular check-ups. Furthermore, the technology could detect suspicious tumours that generate a specific terahertz ‘fingerprint’.”

Terahertz technologies are currently being used in security scan systems at airports as well as industrial and clinical applications. The ANU physicists and their colleagues in the UK have found a way to greatly enhance the amount of information that their devices can obtain about an object compared to these technologies.

“In today’s technologies, usually only the intensity of the terahertz radiation is detected. However, we’ve been able to detect other changes in its properties such as polarisation as the terahertz pulse passes through and interacts with a material or object. By detecting the polarisation of the pulse, we can uncover more information about the material,” Professor Fu said.

“Polarisation is essentially the directions in which the electromagnetic wave vibrates as it travels.”

Co-researcher Professor Hoe Tan said the team’s work uses nanotechnology which results in a smaller footprint than today’s technology, thereby offering potential cost-savings.

“We could see our little devices being used to make security screening at airports easier and less intrusive – wouldn’t it be nice to have a sophisticated scanning system whereby we wouldn’t need to queue at airports, and take our laptops and liquids out from our carry-on bags,” said Professor Tan from the ANU Research School of Physics.

The research builds on a long-term collaboration between the ANU group, led by Distinguished Professor Chennupati Jagadish, and an Oxford University group, led by Professor Michael Johnston, with the support of Australian Research Council (ARC), Australian National Fabrication Facility, and the Australian Government International Postgraduate Research Scholarship.

“We are currently further developing the packaging and control electronics of the device so that it is compatible with commercial rather than just lab-based terahertz spectrometers and imaging systems,” Professor Jagadish said.

“We are also excited about using the detectors in the discovery of new artificial materials as part of the new ARC Centre of Excellent for Transformative Meta-Optical Systems hosted at ANU.”

The research is published in Science. The lead author of the paper, Dr Kun Peng, who is currently a postdoctoral fellow at Oxford, was a PhD student within the ANU team and graduated in 2017.

Three-dimensional cross-nanowire networks recover full terahertz state

KUN PENG, DIMITARS JEVTICS, FANLU ZHANG, SABRINA STERZL, DJAMSHID A. DAMRY, MATHIAS U. ROTHMANN, BENOIT GUILHABERT, MICHAEL J. STRAIN, HARK H. TAN, LAURA M. HERZ, LAN FU, MARTIN D. DAWSON, ANTONIO HURTADO, CHENNUPATI JAGADISH, AND MICHAEL B. JOHNSTON

Science, 1st May 2020

Terahertz (THz) radiation is an interesting region of the electromagnetic spectrum lying between microwaves and infrared. Non-ionizing and transparent to most fabrics, it is finding application in security screening and imaging but is also being developed for communication and chemical sensing. To date, most THz detectors have focused just on signal intensity, an effort that discards half the signal in terms of the full optical state, including polarization. Peng et al. developed a THz detector based on crossed nanowires (arranged in a hash structure) that is capable of resolving the full state of the THz light. The approach provides a nanophotonic platform for the further development of THz-based technologies.