Researchers show off 'Harry Potter' style invisibility cloak

Following mathematical guidelines devised in 2006 by physicists in the UK, engineers at Purdue University have created a theoretical design capable of bending light around the object being cloaked.

The design, which resembles a round hairbrush, uses an array of tiny needles radiating outwards from a central spoke.

The object surrounded by the cylindrical array of nano-needles would be invisible, according to Vladimir Shalaev, Purdue's Robert and Anne Burnett Professor of Electrical and Computer Engineering.

Shalaev admitted that the design has a major limitation in that it works only for a single wavelength, and not for the entire frequency range of the visible spectrum.

"But this is a first design step towards creating an optical cloaking device that might work for all wavelengths of visible light," he said.

The calculations indicate the device would make an object invisible in a wavelength of 632.8 nanometres, which corresponds to the colour red.

The same design, however, could be used to create a cloak for any other single wavelength in the visible spectrum, Shalaev claimed.

"How to create a design that works for all colours of visible light at the same time will be a big technical challenge, but we believe it is possible," he said. "In principle, this cloak could be as large as a person or an aircraft."

Research findings are detailed in a paper appearing this month in Nature Photonics.

The paper was co-authored by doctoral students Wenshan Cai and Uday K. Chettiar, research scientist Alexander V. Kildishev and Shalaev.

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