Monday, April 09, 2007

Engineers Bring 'Invisibility' One Step Closer to Reality

Technological Hocus Pocus

RED ORBIT - April 2, 2007

Researchers using nanotechnology have taken a step toward creating an "optical cloaking" device that could render objects invisible by guiding light around anything placed inside this "cloak."

The Purdue University engineers, following mathematical guidelines devised in 2006 by physicists in the United Kingdom, have created a theoretical design that uses an array of tiny needles radiating outward from a central spoke. The design, which resembles a round hairbrush, would bend light around the object being cloaked. Background objects would be visible but not the object surrounded by the cylindrical array of nano-needles, said Vladimir Shalaev, Purdue's Robert and Anne Burnett Professor of Electrical and Computer Engineering.

The design does, however, have a major limitation: It works only for any single wavelength, and not for the entire frequency range of the visible spectrum, Shalaev said.

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

Research findings are detailed in a paper appearing this month in the journal Nature Photonics. The paper, which is appearing online this week, was co-authored by doctoral students Wenshan Cai and Uday K. Chettiar, research scientist Alexander V. Kildishev and Shalaev, all in Purdue's School of Electrical and Computer Engineering.

Calculations indicate the device would make an object invisible in a wavelength of 632.8 nanometers, which corresponds to the color red. The same design, however, could be used to create a cloak for any other single wavelength in the visible spectrum, Shalaev said.

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

The research is based at the Birck Nanotechnology Center at Purdue's Discovery Park. - - - -


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