NSF – While no one yet has the power to put on a garment and disappear, Elena Semouchkina, an associate professor of electrical and computer engineering at Michigan Technological University, has found ways to use magnetic resonance to capture rays of visible light and route them around objects, rendering those objects invisible to the human eye. Her work is based on the transformation optics approaches, developed and applied to the solution of invisibility problems by British scientists John B. Pendry and Ulf Leonhardt in 2006.
“Imagine that you look at the object, which is placed in front of a light source,” she explains.
“The object would be invisible for your eye if the light rays are sent around the object to avoid scattering, and are accelerated along these curved paths to reach your eye undistinguishable from direct straight beams exiting the source, when the object is absent.”
At its simplest, the beams of light flow around the object and then meet again on the other side so that someone looking directly at the object would not be able to see it–but only what’s on the other side.
“You would see the light source directly through the object,” said Semouchkina. “This effect could be achieved if we surround the object by a shell with a specific distribution of such material parameters as permittivity and permeability.”
She and her collaborators at the Pennsylvania State University, where she is also an adjunct professor, designed a nonmetallic “invisibility cloak” that uses concentric arrays of identical glass resonators made of chalcogenide glass, a type of dielectric material–that is, one that does not conduct electricity.
Multi-resonator structures comprising Semouchkina’s invisibility cloak belong to “metamaterials”–artificial materials with properties that do not exist in nature–since they can refract light by unusual ways. In particular, the “spokes” of tiny glass resonators accelerate light waves around the object making it invisible.
Until recently, there were no materials available with the relative permeability values between zero and one, which are necessary for the invisibility cloak to bend and accelerate light beams, she said. However, metamaterials, which were predicted more than 40 years ago by the Russian scientist Victor Veselago, and first implemented in 2000 by Pendry from Imperial College, London, in collaboration with David R. Smith from Duke University, now make it possible, she said.
Metamaterials use lattices of resonators, instead of atoms or molecules of natural materials, and provide for a broad range of relative permittivity and permeability including zero and negative values in the vicinity of the resonance frequency, she said. Metamaterials were listed as one of the top three physics discoveries of the decade by the American Physical Society. more> http://tinyurl.com/4duw7o6
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