'T-ray' signals for developing next generation security sensors

London, Feb 6 : A new research into a type of radiation known as T-rays may soon be led to the development a new generation of sensors for detecting explosives and poisons.

T-rays are electromagnetic waves in the far infrared part of the electromagnetic spectrum that have a wavelength 500 times longer than visible light,

This study, performed by a team of UK and Spanish physicists led in the UK by Dr Stefan Maier from Imperial College London's Department of Physics, and Dr Steve Andrews of the University of Bath, indicated that the T-rays can be guided along the surface of a specially designed material, known as a metamaterial.

A metamaterial is a man-made material with designed electromagnetic properties which are impossible for natural materials to possess.

In order to use T-rays in many real world applications, it was essential to control T-rays in this manner. According to the researchers, security sensing and scanning are one of the most potential areas for the use of T-rays, because many of the molecules in explosives and biological agents like anthrax strongly absorb this radiation.

When T-rays are tightly confined on surfaces in contact with such molecules, there is a dramatic increase in the detection sensitivity.

Earlier, simple metallic surfaces had been used to control T-ray propagation; however, they only weakly guide the radiation, which extended as a weak field many centimetres above the surface of the material, thus making it less effective for sensing.

It has been shown by the new study that a metamaterial surface brings T-rays close to it, and creates a very strong field less than a millimetre above the surface.

This results in a significant enhancement in the absorption by molecules on the surface making highly effective sensing techniques possible.

"T-rays have the potential to revolutionise security screening for dangerous materials such as explosives. Until now it hasn't been possible to exert the necessary control and guidance over pulses of this kind of radiation for it to have been usable in real world applications. We have shown with our material that it is possible to tightly guide T-rays along a metal sheet, possibly even around corners, increasing their suitability for a wide range of situations," Dr Maier explained the importance of their metamaterial.

The researchers created the metamaterial for this new research that consisted of a metallic surface textured with a two-dimensional arrangement of pits. The dimensions of the pits were chosen so that T-rays are drawn closely to them as they travel along the surface.

Dr Andrews said that even though the results of their study are quite promising, more work is required to refine the technology before such surfaces can be used for sensing applications.

"At the moment only a small number of the frequencies that make up a pulse of T-ray radiation are closely confined by our metamaterial. More sophisticated designs are needed in order to make sure that the whole pulse is affected by the surface structure, so that absorption features of molecules can be clearly identified," he said.

The study was published recently in Nature Photonics.

ANI