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Invisibility cloak one step closer, scientists say
(Agencies)
Updated: 2008-08-11 10:31 For a metamaterial to produce negative refraction, it must have a structural array smaller than the wavelength of the electromagnetic radiation being used. This was done using microwaves in 2006 by David Smith of Duke University in North Carolina and John Pendry of Imperial College London. Visible light is harder. Some groups managed it with very thin layers, virtually only one atom thick, but these materials were not practical to work with and absorbed a great deal of the light directed at it. "What we have done is taken that material and made it much thicker," Valentine said. His team, whose work is reported in Nature, used stacked silver and metal dielectric layers stacked on top of each other and then punched through with holes. "We call it a fishnet," Valentine said. The other team, reporting in Science, used an oxide template and grew silver nanowires inside porous aluminum oxide at tiny distances apart, smaller than the wavelength of visible light. This material refracts visible light. Immediate applications might be superior optical devices, Valentine said -- perhaps a microscope that could see a living virus. "However, cloaking may be something that this material could be used for in the future," he said. "You'd have to wrap whatever you wanted to cloak in the material. It would just send light around. By sending light around the object that is to be cloaked, you don't see it." |
