An international team of scientists from Denmark and the UK (Technical University of Denmark, Imperial College London, and the University of Birmingham, UK) have designed an invisibility cloak — and one that doesn’t need to be a lot larger than its target, like previous models did.
The team used a technology called “carpet cloaks”, a reference to their relatively smaller size compared to similar technologies. This was made possible by using metamaterials — ones not normally found in nature.
The metamaterial uses a grating pattern of alternating layers; this pattern channels light of a certain wavelength around the object, making it appear as if there is in fact a flat plane in its place. The grates, or openings — which are nano-sized — restore the path of light, essentially disguising the object from interacting with the beam and thereby being revealed.
The team published a paper in the Optical Society’s journal: Optics Express. The paper is available for free viewing. Jingjing Zhang (Denmark University’s Fotonik Department of Photonics Engineering and Structured Electromagnetic Materials), postdoctoral student and one of the authors of the paper says that:
The cloak parameters can be tweaked by tuning the filling factor and the orientation of the layers. Therefore, layered materials bypass the limitation of natural materials at hand and give us extra freedom to design the devices as desired.
The filling factor is the size of the gratings — meaning that this carpet cloak can be modified to bend different wavelengths of light around objects, such as infrared or visible, among others.
ScienceDaily writes that the cloak is easier to manufacture than previous designs, giving the work added advantages over its predecessors. The cloak itself is invisible to infrared light — after all, what good would it be if the bad guys knew you were using it?
The beam is currently slightly less intense after passing around the carpet cloak, something the team will work to eradicate in future models. Zhang mentions that:
Although our experiment was carried out at near-infrared frequencies, this design strategy is applicable in other frequency ranges. We anticipate that with more precise fabrication, our technique should also yield a true invisibility carpet that works in the microwave and visible parts of the spectrum and at a larger size — showing promise for many futuristic defense and other applications.