Bringing T-Rays Under Control

T-rays, terahertz (trillion-cycle-per-second) electromagnetic pulses, are now easier to control and, possibly, to use for development of innovative diagnostic and therapeutic technologies:

Researchers at the University of Bath, UK, and in Spain have said they have found a way to control the flow of terahertz radiation down a metal wire. Their findings are set out in a letter published in the current journal Physical Review Letters.
Terahertz radiation, whose frequency is around one thousand billion cycles a second, bridges the gap between the microwave and infrared parts of the electromagnetic spectrum.
Materials interact with radiation at T-ray frequencies in different ways than with radiation in other parts of the spectrum, making T-rays potentially important in detecting and analysing chemicals by examining how they absorb T-rays fired at them.
This would allow quality control of prescribed drugs and detection of explosives to be carried out more easily, as many complex molecules have distinctive ‘signatures’ in this part of the electromagnetic spectrum.
T-ray applications are presently limited by the relatively poor ability to focus the rays, which is achieved using the conventional means of lenses and mirrors to focus the radiation. This limits the spot size of focused T-rays to a substantial fraction of a millimetre and this has made studies of small objects such as biological cells with high resolution are virtually impossible.
But in their work, the researchers found that although ordinary metal wire would not guide T-rays very well, if a series of tiny grooves was cut into the wire, it would do so much more effectively. If such a corrugated metal wire is then tapered to a point it becomes possible to very efficiently transport radiation to a point as small as a few millionths of a metre across.
This might, for example, lead to breakthroughs in examining very small objects such as the interior of biological cells where it might be possible to detect diseases or abnormalities. T-rays could also be directed to the interior of objects which could be useful in applications like endoscopic probing for cancerous cells or explosive detection.
“This is a significant development that would allow unprecedented accuracy in studying tiny objects and sensing chemicals using T-rays” said Dr Stefan Maier, of the University of Bath’s Department of Physics.

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