New method to focus T-rays could lead to breakthrough in disease
3 November 2006
Bath, UK. A breakthrough in the harnessing of T-rays
could dramatically improve the detecting and sensing of objects as varied as
biological cell abnormalities and explosives.
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 issue
of Physical Review Letters.
T-rays are electromagnetic radiation in
the terahertz frequency range (1012 hertz, about 1mm wavelength)
and bridge the gap between the microwave and infrared parts of the 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
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.
“Metal wire ordinarily has a limited ability to
allow T-rays to flow along it, but our idea was to overcome this by
corrugating its surface with a series of grooves, in effect creating an
artificial material or ‘metamaterial’ as far as the T-rays are concerned.”
“In this way, the T-rays can be focused to the tip of the wire and guided
into confined spaces or used to detect small objects, with important
implications for disease detection or finding explosive that are hidden.”
Dr Maier is working with Dr Steve Andrews at Bath, and with Professor
Francisco García-Vidal, of the Universidad Autónoma de Madrid, and Luis
Martín-Moreno, of the Universidad de Zaragoza-CSIC.
The project, which is
funded by the Royal Society in the UK, the EU and the US Airforce, is one
year into its three-year term. The researchers hope to produce a working
model within a year.