Saturday, 28 January 2012

Plasmonic cloak makes objects invisble, but only in the microwave region of the spectrum

Researchers have "cloaked" a three-dimensional object, making it invisible from all angles, for the first time.

Source: Engadget - USS Defiant
However, the demonstration works only for waves in the microwave region of the electromagnetic spectrum.

It uses a shell of what are known as plasmonic materials; they present a "photo negative" of the object being cloaked, effectively cancelling it out. The idea, outlined in New Journal of Physics, could find first application in high-resolution microscopes.

Most of the high-profile invisibility cloaking efforts have focused on the engineering of "metamaterials" - modifying materials to have properties that cannot be found in nature. The modifications allow metamaterials to guide and channel light in unusual ways - specifically, to make the light rays arrive as if they had not passed over or been reflected by a cloaked object.

Previous efforts that have made 3-D objects disappear have relied upon a "carpet cloak" idea, in which the object to be cloaked is overlaid with a "carpet" of metamaterial that bends light so as to make the object invisible. 

Now, Andrea Alu and colleagues at the University of Texas at Austin have pulled off the trick in "free space", making an 18cm-long cylinder invisible to incoming microwave light.