Washington: Turning science fiction and fantasy into a stunning reality, scientists from the US Department of Energy (DOE)’s Berkeley Lab and University of California (UC)-Berkeley have devised the first-ever ultra-thin invisibility “skin” cloak that can conform to the shape of an object and conceal it from detection with visible light.
Although the cloak is only microscopic in size, the principles behind the technology should enable it to be scaled-up to conceal macroscopic items as well.
Working with brick-like blocks of gold nanoantennas, the Berkeley researchers “fashioned a “skin” cloak barely 80 nanometers in thickness.
It was wrapped around a 3D object about the size of a few biological cells and arbitrarily shaped with multiple bumps and dents.
The surface of the skin cloak was meta-engineered to reroute reflected light waves so that the object was rendered invisible to optical detection when the cloak is activated.
“This is the first time a 3D object of arbitrary shape has been cloaked from visible light,” said Xiang Zhang, director of Berkeley Lab’s Materials Sciences Division and a world authority on metamaterials.
“Our ultra-thin cloak now looks like a coat. It is easy to design and implement, and is potentially scalable for hiding macroscopic objects,” he said in a paper that appeared in the journal Science.
It is the scattering of light – be it visible, infrared or X-ray – from its interaction with matter that enables us to detect and observe objects.
For the past 10 years, Zhang and his research group have been pushing the boundaries of how light interacts with metamaterials, managing to curve the path of light or bend it backwards — phenomena not seen in natural materials — and to render objects optically undetectable.
In the Berkeley study, when red light struck an arbitrarily-shaped 3D sample object in area that was conformally wrapped in the gold nanoantenna skin cloak, the light reflected off the surface of the skin cloak was identical to light reflected off a flat mirror, making the object underneath it invisible even by phase-sensitive detection.
The cloak can be turned “on” or “off” simply by switching the polarisation of the nanoantennas.
“A phase shift provided by each individual nanoantenna fully restores both the wavefront and the phase of the scattered light so that the object remains perfectly hidden,” explained co-lead author Zi Jing Wong.
The ability to manipulate the interactions between light and metamaterials offers future prospects for technologies such as high resolution optical microscopes and superfast optical computers.
Invisibility skin cloaks on the microscopic scale might prove valuable for hiding the detailed layout of microelectronic components or for security encryption purposes.
At the macroscale, among other applications, invisibility cloaks could prove useful for 3D displays.
First Published | 18 September 2015 12:19 PM