Boffins one step closer to invisible shed

Successfully cloak 3D object from microwaves

Invisibility-investigating boffins have managed for the first time to cloak a three-dimensional object in free space – but only from microwaves.

Credit: D Rainwater et al 2012
New Journal of Physics (click to enlarge)

Rather than bending light around the object, an 18cm cylindrical tube, the researchers used "plasmonic cloaking", which uses metamaterials that don't reflect light in the same way as an object.

"When the scattered fields from the cloak and the object interfere, they cancel each other out and the overall effect is transparency and invisibility at all angles of observation," study co-author Professor Andrea Alu said in a canned statement.

But don't get too excited yet, the boffins only successfully fooled waves in the microwave section of the electromagnetic spectrum. They have yet to have any success with visible light.

The cloak gave the best results when the microwaves were at a frequency of 3.1 gigahertz and over a moderately broad bandwidth. The shape of the object being cloaked behind the plasmonic stuff is irrelevant, but size does matter.

"In principle, this technique could be used to cloak light; in fact, some plasmonic materials are naturally available at optical frequencies.

"However, the size of the objects that can be efficiently cloaked with this method scales with the wavelength of operation, so when applied to optical frequencies we may be able to efficiently stop the scattering of micrometre-sized objects," Alu said.

So the best they can do at the moment is think about possibly properly making a microscope tip invisible, which would be good for biomedical and optical near-field reasons, but not terribly exciting for those hoping to wander around Hogwarts with impunity.

The research was published today in the New Journal of Physics, and is available as a PDF here. ®

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