Earlier: [1], [2]. [1] http://groups.yahoo.com/group/silk-list/message/7033 [2] http://groups.yahoo.com/group/silk-list/message/28575
http://www.gizmag.com/invisibility-cloak-made-of-glass/15796/ Researchers working on an invisibility cloak made of glass By Darren Quick 00:32 July 22, 2010 We’ve covered a few different research efforts looking to develop “invisibility cloak” technology on Gizmag, including 3D metamaterials that negatively refract visible and near-infrared light and U-shaped “nano-rings” that manipulate light. The latest news sure to get Harry Potter fans excited comes out of Michigan Technical University where Elena Semouchkina, an associate professor of electrical and computer engineering, has found ways to use magnetic resonance to capture rays of visible light and route them around objects, rendering them invisible to the human eye. Semouchkina and colleagues at the Pennsylvania State University, where she is also an adjunct professor, describe developing a nonmetallic cloak that uses identical glass resonators made of chalcogenide glass, a type of dielectric material (one that does not conduct electricity). In computer simulations, the cloak made objects hit by infrared waves – approximately one micron or one-millionth of a meter long – disappear from view. Earlier attempts by other researchers used metal rings and wires. “Ours is the first to do the cloaking of cylindrical objects with glass,” Semouchkina said. Like most other “invisibility cloak” research, Semouchkina’s uses metamaterials, which are artificial materials having properties that do not exist in nature. Hers are made of tiny glass resonators arranged in a concentric pattern in the shape of a cylinder. The “spokes” of the concentric configuration produce the magnetic resonance required to bend light waves around an object, making it invisible. Metamaterials, which use small resonators instead of atoms or molecules of natural materials, straddle the boundary between materials science and electrical engineering. They were named one of the top three physics discoveries of the decade by the American Physical Society. Semouchkina and her team now are testing an invisibility cloak re-scaled to work at microwave frequencies and made of ceramic resonators. They’re using Michigan Tech’s anechoic chamber, a cave-like compartment in an Electrical Energy Resources Center lab, lined with highly absorbent charcoal-gray foam cones. There, antennas transmit and receive microwaves, which are much longer than infrared light, up to several centimeters long. They have cloaked metal cylinders two to three inches in diameter and three to four inches high. That’s not exactly big enough to hide junior wizards, but an impressive feat nonetheless. “Starting from these experiments, we want to move to higher frequencies and smaller wavelengths,” the researcher said. “The most exciting applications will be at the frequencies of visible light.” So one day, could the police cloak a swat team or the Army, a tank? “It is possible in principle, but not at this time,” Semouchkina said. The team recently reported on their research in the journal Applied Physics Letters. -- ((Udhay Shankar N)) ((udhay @ pobox.com)) ((www.digeratus.com))
