Physicist tailors wideband invisibility cloak

Posted by Aharon Etengoff

San Francisco (CA) - Fractal Antenna has developed a system capable of switching a wideband invisibility cloak on and off. According to inventor Nathan Cohen, the device 'sets a path' for the realization of a practical invisibility cloak that will allow hidden objects to 'see' with the flick of a switch.

"Previous cloak descriptions had a fatal flaw that no one knew how to address: when you cloak you also make the object 'blind' as well. Of course, you can physically remove the cloak, but that is totally impractical," said Cohen. "What we've been working on for some time are ways of changing the electromagnetic characteristics of the cloak, on the fly, and that changes the cloak into a kind of lens, that you then can see out of. Since the switching can be done rapidly, the invisibility cloak can blink on and off at will and is a 'cloak-on-command.'"

Physicist tailors wideband invisibility cloak

Cohen explained that his firm had pioneered and demonstrated the world's first practical invisibility cloak, which operates on the basis of microwaves. He noted that previous and more recent invisibility cloaks were either too narrow in frequency range (and thus impractical) or merely mirrors with a corrective set of layers that removed the mirror's reflected distortions.

"I still haven't figured out the advantage of calling a mirror a 'cloak' — who wants to hide behind a mirror - but that's what many other scientists find curiously exciting...[There is]  no smoke and no mirrors here."

Cohen added that his invisibility technology is built around the concept of closely packed fractal resonators - a fractal metamaterial - that uniquely enables the cloak's operation. 

Physicist tailors wideband invisibility cloak

However, Cohen cautioned that the current generation of invisibility cloaks do not work at visible light, except on pinhead sized scales.

"People have high expectations, despite our continued cautions that Harry Potter and Klingons aren't lurking in the shadows. [Our] firm sees practical uses of invisibility cloaking for defense, telecom, and energy needs, mostly at microwave and IR wavelengths, with later applications at visible wavelengths in the future."

See also

Cloak of invisibility to aid semi business
Gold rings show first hint of true cloaking ability
Scientists create 'invisibility' cloak that bends microwaves