Scientists have developed a new way to create electromagnetic Terahertz (THz) waves (T-rays) — the technology behind full-body security scanners. Their new stronger and more efficient continuous wave T-rays could be used to make better medical scanning gadgets and may one day lead to innovations similar to the Tricorder scanner used in Star Trek.

In the study, researchers from the Institute of Materials Research and Engineering (IMRE), a research institute of the Agency for Science, Technology and Research (A*STAR) in Singapore, and Imperial College London have made T-rays into a much stronger directional beam than was previously thought possible, and at room-temperature conditions.

This a breakthrough should allow future T-ray systems to be smaller, more portable, easier to operate, and much cheaper than current devices.

The scientists say that the T-ray scanner and detector could provide part of the functionality of a portable sensing, computing and data communications device — since T rays (which are safer than x-rays) are capable of detecting biological phenomena such as increased blood flow around tumorous growths. Future scanners could also perform fast wireless data communication to transfer a high volume of information on the measurements it makes.

T-rays are radiation in the far-infrared part of the electromagnetic spectrum with a wavelength hundreds of times longer than those that make up visible light. Such waves are already in use in airport security scanners, prototype medical scanning devices, and in spectroscopy systems for materials analysis. T-rays can sense molecules such as those present in cancerous tumors and living DNA, since every molecule has its unique signature in the THz range. They can also be used to detect explosives or drugs, for gas pollution monitoring or non-destructive testing of semiconductor integrated circuit chips.

Current T-ray imaging devices are very expensive and operate at low output power, since creating them consumes large amounts of energy and needs to take place at very low temperatures.

How to create T-rays at low cost

The researchers demonstrated that it is possible to produce a strong beam of T-rays by shining light of differing wavelengths on a pair of electrodes — two pointed strips of metal separated by a 100 nanometer gap on top of a semiconductor wafer.

The structure of the tip-to-tip nano-sized gap electrode greatly enhances the THz field and acts like a nanoantenna to amplify the wave generated. In this method, THz waves are produced by an interaction between the electromagnetic waves of the light pulses and a powerful current passing between the semiconductor electrodes. The scientists are able to tune the wavelength of the T-rays to create a beam that is useable in the scanning technology.

Lead author Dr Jing Hua Teng, from A*STAR’s IMRE, said: “The secret behind the innovation lies in the new nanoantenna that we had developed and integrated into the semiconductor chip.” Arrays of these nanoantennas create much stronger THz fields that generate a power output that is 100 times higher than the power output of commonly used THz sources using conventional antenna structures. A stronger T-ray source gives the T-ray imaging devices more power and higher resolution.

“T-rays promise to revolutionize medical scanning to make it faster and more convenient, potentially relieving patients from the inconvenience of complicated diagnostic procedures and the stress of waiting for accurate results,” said research co-author Stefan Maier, a visiting scientist at A*STAR’s IMRE and Professor in the Department of Physics at Imperial College London.

“Thanks to modern nanotechnology and nanofabrication, we have made a real breakthrough in the generation of T-rays that takes us a step closer to these new scanning devices. We have been able to make amplified waves at the key wavelength of 1000 micrometers that can be used in such real-world applications.”

Ref.: H. Tanoto et al., Greatly enhanced continuous-wave terahertz emission by nano-electrodes in a photoconductive photomixer, Nature Photonics, 2012 [DOI: 10.1038/nphoton.2011.322]