August 9, 2011

Invisibility Cloak Closer To Reality

Despite becoming a popular idea through science fiction, fantasy novels and films, a cloak that renders its wearer invisible is usually dismissed as impossible. However this does not dissuade some researchers from exploring the idea of it, International Business Times is reporting.

An undergraduate student has published a study that could open up the possibility for a potential invisibility cloak wearer to move around amongst ever-changing backgrounds of a variety of colors.

Under the guidance of Professor Ulf Leonhardt, Janos Perczel, originating from Hungary and reading Logic, Philosophy of Science and Physics at the University of St. Andrews, has overcome a major hurdle in the development of invisibility cloaks by adding an optical device into their design that not only remains invisible itself, but also has the ability to slow down light.

For an object to literally vanish before a person's eyes, a cloak would have to simultaneously interact with all of the wavelengths, or colors, that make up light. An invisibility cloak works by diverting light within it so that the light avoids a certain volume or void within which an object could be placed, says a report in the New Journal of Physics.

The cloak's task is to reshape the light in such a way that the light illuminates the space as though the cloak (and the object it shields) weren't there. When the light is bent, it engulfs the object, much like water covering a rock sitting in a river bed, and carries on its path making it seem as if nothing is there.

Light, however, can only be accelerated to a speed faster than it would travel in space under certain conditions, and this restricts invisibility cloaks to work in a limited part of the spectrum, essentially just one color.

This would be ideal if somebody was planning to stand still in camouflage; however, the moment that they start to move the scenery will begin to distort, revealing the person under the cloak. By slowing all of the light down with an invisible sphere, it does not need to be accelerated to such high speeds and can therefore work in all parts of the spectrum.

Perczel said, "I started to work on the problem of superluminal propagation as Professor Leonhardt's summer student with an EPSRC grant. Once the idea was present, I worked for over eight months to overcome the technical barriers and to make the proposal practicable."

An Institute of Physics spokesperson said, "This new development opens up further possibilities for the design of a practical invisibility cloak, overcoming the problem of light speed that other advances have struggled to address and, very impressively, this significant advance was achieved by an undergraduate student."


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