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Jack, having hitherto been successful in all his undertakings, resolved not to be idle in future; he therefore furnished himself with a horse, a cap of knowledge, a sword of sharpness, shoes of swiftness, and an invisible coat, the better to perform the wonderful enterprises that lay before him. from The History of Jack the Giant-Killer The Blue Fairy Book |
The race to build an exotic material with a negative refractive index for visible light has been won by a team of researchers in Germany. The demonstration could open the door to a new generation of optical devices such as superlenses able to see details finer then the wavelength of visible light.
It may also, ultimately, lead to further breakthroughs in "invisibility cloaks" which could hide objects from the human eye.
Light waves consist of alternating electric and magnetic fields that interact with materials as they travel, or propagate. This interaction determines a property of the material called its refractive index, which is a measure of the behaviour of light as it passes through the material. The refractive index describes the way the light waves bend when they enter and leave the material and the speed at which they propagate.
The refractive
index of normal materials is always positive – 1.0003 in air, about
1.5 in ordinary glass, 2.1 in zircon, and 2.4 in diamond. In the mid-1990s,
however, John Pendry of Imperial College London, UK, realised that it
was possible to construct artificial materials in which the refractive
index could be negative.
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