Scientists and Engineers are once again making fantasy a reality, having developed a functional nanoscale invisibility cloak.
Using blocks of gold nanoantennas, researchers created a “skin cloak” nearly 80 nanometers in thickness. The cloak was wrapped around a 3D object 1,300 square microns in size. The cloak then refracts the light that hits its surface, rendering the cloak, and therefore the object inside, invisible.
The cloak can be turned on or off by switching the polarization of the nanoantennas, as shown in the video below.
“This is the first time a 3D object of arbitrary shape has been cloaked from visible light,” said Xiang Zhang, lead author of the paper and director of Berkeley Lab’s Materials Sciences Division. “Our ultra-thin cloak now looks like a coat. It is easy to design and implement and is potentially scalable for hiding macroscopic objects.”
Zhang’s team have been experimenting with how light interacts with metamaterials (artificial nanostructures with electromagnetic properties) for a decade now.
In past experiments, metamaterial-based “carpet” cloaks were bulky, hard to scale up and couldn’t provide complete invisibility.
“Creating a carpet cloak that works in air was so difficult we had to embed it in a dielectric prism that introduced an additional phase in the refracted light, which made the cloak visible by phase-sensitive detection,” said co-lead author Xingjie Ni, affiliated with the National Science Foundation Nanoscale Science and Engineering Center.
“Recent developments in metasurfaces however, allow us to manipulate the phase of a propagating wave directly through the use of subwavelength-sized elements that locally tailor the electromagnetic response at the nanoscale, a response that is accompanied by dramatic light confinement.”
Currently limited to the small scale, invisibility technology is nowhere near what some may claim.
Possible applications for the technology at this scale are hard to imagine, and if properly scaled up it’s hard to think of non-military uses. Do we really want invisibility cloaks? Do we really need them?
As the technology develops, we’ll have to see what commercial applications are devised, but they will no doubt be security related.
Recently published in Science, the paper is available here.