Step inside and, at least at a certain wavelength, light would flow smoothly around you as though you were hardly there — that was thinking behind the world’s first “invisibility cloak” which was unveiled a couple of years ago. The catch was that, with no light entering the cloak, the inability of people to see you on the inside would be matched by your inability to see them on the outside.
Now, a team led by Che Ting Chan at the Hong Kong University of Science and Technology claims to have solved this problem with a theoretical device that can cloak an object from a distance. The idea is that the cloak uses an in-built copy of the object to control how the cloak cancels the external scattering of electromagnetic waves. When light shines on the cloak and the remote object, both of them are invisible.
Light geometry
The invisibility cloaks built since 2006 have been based on a shell of material with a non-uniform, negative refractive index to guide light in curved lines. But it is not easy to figure out how to design the shell’s refractive-index profile so that the light can propagate neatly around a finite volume. The trick is to see the material as something that can perform a transform from cartesian co-ordinates, in which light travels in straight lines, to curved co-ordinates. Coupled with James Clerk Maxwell’s theory of electromagnetism, such transforms can provide a blueprint for a device that leaves a “hole” in space.
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http://physicsworld.com/cws/article/news/36633;jsessionid=6126CBB2C9E5462D037FE0F91EAD0480