[November 13, 2012]

Inventor Casts Doubt on Perfect Cloak

Recent reports of a 'perfect' invisibility cloak have attracted great attention. But Nathan Cohen, inventor of the invisibility cloak, finds the perfect cloak far from perfect.

Cohen is a physicist and imaging expert and the recognized inventor of invisibility cloak technology through issuance of U.S. patent number 8,253,639, the world's first and only invisibility cloak patent. Cohen and his team at Fractal Antenna Systems have spent several years bringing invisibility cloaks to reality, using technology derived from fractal antenna technology. With the most experience and innovation of any research and development effort, the team has produced wideband, high fidelity, thin invisibility cloaks, and recently announced breakthrough embodiments that cloaked a man, and also acted as a 'deflector shield'.

Cohen's opinion on the claims of a perfect cloak is one of disappointment. "The results of the Duke University group illuminate no new avenues on improving the extant invisibility cloak technology."

Cohen asserts that the'perfect cloak' has vast limitations. "If you move half a degree in angle, it stops working. If you move ½ a percent in bandwidth, it stops working. Even when in exact alignment, there are variations in intensity that, according to their data, change by almost 50%. Furthermore the 'perfect cloak' has to have a huge superstructure of two different sets of mirrors and is more than twice as wide as the region being cloaked. So by attempting to disappear at one super-narrow wavelength you actually increase your profile at all others. It makes you more, not less, visible"

According to Cohen, an effort to cloak a tank with a 'perfect cloak' would require a contraption surrounding it as big as an Olympic swimming pool, with a cowling arrangement that would make it look like a huge jet engine intake. "If you move a bit off axis, you are toast, even at that one super-narrow microwave band."

Cohen's team has produced high fidelity wideband cloaking. "By avoiding the quest for 'perfect' we find huge leeway in 'very, very good'. That is where the progress in cloaks has been achieved and where it will continue to go," said Cohen.

Cohen will be demonstrating the invisibility cloak technology at the Radio Club of America in New York City on November 16, 2012.

ABOUT FRACTAL ANTENNA SYSTEMS, INC.

Fractal Antenna Systems, Inc. ( http://www.fractenna.com ) supplies products for the world's most demanding wireless, and electromagnetic applications. Backed by over three dozen U.S., and international patents, plus dozens of patents pending, Fractal Antenna Systems is the recognized pioneer in fractal technology, with extensive research and field experience over 18 years in business. The company is a privately held and headquartered in Waltham, Massachusetts, USA.

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