New sensors to use nano directed sub mm rays

Academic researchers have established a good way of directing T-Rays using nano structured materials. There has been much interest in using T-Rays - terahertz frequency radiation in the 0.1mm to 1mm wave band – for security scanning, because many of the molecules in explosives and biological agents like anthrax strongly absorb it. If T-rays are tightly confined on surfaces in contact with such molecules then the detection sensitivity is greatly increased. Simple metallic surfaces have been used to control T-ray propagation before, but these only weakly guide the radiation, which extends as a weak field many centimetres above the surface of the material, thus rendering it less effective for sensing. A new study 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 has shown that metal with a nanostructured surface made up of tiny pits, which the developers call, “Metamaterial”draws T-rays close to it, creating a very strong field less than a millimetre above the surface. This greatly enhances the absorption by molecules on the surface making highly effective sensing techniques possible. According to Dr Maier, "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 Andrews says that although the results of their study are very promising, more work is needed 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." Dr Maier and Dr Andrews designed the metamaterial together with colleagues from Universities in Madrid and Zaragoza, with financial support from the US Air Force and the Royal Society. Their breakthrough is based on previous theoretical predictions obtained by the Spanish team together with Imperial's Professor John Pendry, published in Science in 2004. For more information: Email Danielle Reeves