Invisibility cloak makes small objects disappear, military uses envisaged
Fri 18 Sep 2015
Researchers are developing an invisibility cloak which conforms to the shape of an object and hides it in visible light.
The microscopic material, developed by a team of scientists at the University of California (UC) Berkeley and the U.S. Department of Energy’s (DoE) Berkeley National Laboratory, is made from an ultra-thin 80 nanometre layer of gold rectangular nanoantennae from which the light is reflected.
Until now, optical fabrics used to obscure objects would rely on volumetric properties to gradually bend light, but these proved bulky, difficult to scale up and often unreliable.
“This is the first time a 3D object of arbitrary shape has been cloaked from visible light,” said lead researcher Xiang Zhang, director at 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,” he added.
Published in Science, the paper, An ultrathin invisibility skin cloak for visible light, describes the recent developments made in metasurface technologies. Co-lead author Xingjie Ni explained that the research involved manipulating the phase of a propagating wave through the use of subwavelength-sized elements which modify its electromagnetic response and constrict the amount of light.
The study outlined a test in which red light was directed at a 3D object measuring approximately 1,300 square microns and wrapped in the gold nanoantenna cloak. The scientists found that the object was “perfectly hidden”, with the skin reflecting light from its surface in much the same way as a flat mirror. The invisibility cloak can be turned on and off by changing the polarisation of the nanoantennae.
The technology has sparked great interest in the security community, its microscopic scale and accuracy a potentially valuable technology for encryption. Additionally, once perfected at macro scale, the researchers believe that the technology could be made to conceal objects such as military vehicles and aircraft – or even soldiers themselves.