An extremely thin and much improved cloaking device is designed by scientists using dielectric materials
A new design for a cloaking device surmounting some of the boundaries of existing “invisibility cloaks” has been developed by electrical engineers at the University of California, San Diego.
In the latest study, the researchers designed a cloaking device that is both thin and doesn’t change the brightness of light around a hidden object. More applications than invisibility are in the future for the technology behind this cloak, for example concentrating solar energy and increasing signal speed in optical communications.
Senior writer Boubacar Kanté, professor in the Department of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering, says: “Invisibility may seem like magic at first, but its basic concepts are familiar to everyone. All it requires is a clever handling of our views. Full invisibility still seems beyond reach today, but it might become a reality in the near future thanks to recent progress in cloaking devices.”
As their name implies, cloaks are devices that cover objects to make them appear indiscernible. The idea behind cloaking is to modify the dispersion of electromagnetic waves, such as light and radar, off an object to make it less noticeable to these wave frequencies. But one of the drawbacks of cloaking devices is that they are normally bulky.
First writer Li-Yi Hsu, electrical engineering Ph.D. student at UC San Diego states, “Previous cloaking studies required many layers of materials to secrete an object, the cloak ended up being much thicker than the size of the object being roofed. In this study, we prove that we can use a thin single-layer sheet for cloaking.”
Their hide, the researchers say, also overcomes another basic hitch of existing cloaking devices, being “lossy.” Cloaks that are lossy reflect light at a lower intensity than light striking their surface.
What we have achieved in this study is a ‘lossless’ cloak. It won’t lose any intensity of the light that it reflects,” said Kante.
Many cloaks are lossy because they are made with metal particles, which absorb light. The researchers report that one of the keys to their cloak’s design is the use of non-conductive materials called dielectrics, which unlike metals do not absorb light.
The cloak includes two dielectrics, a proprietary ceramic and Teflon, which are structurally tailored on a very fine scale to change the way light waves reflect off of the cloak.
Just visualize if you saw a sharp drop in brightness around the hidden object, it would be an obvious gossip. This is what happens when you use a lossy cloaking device,” says Kanté. “What we have achieved in this study is a ‘lossless’ cloak. It won’t lose any strength of the light that it reflects.”
“This cloaking device basically fools the observer into thinking that there’s a flat surface,” said Kanté. The study was published in the journal Progress in Electromagnetics Research.
The researchers used Computer-Aided Design software with electromagnetic model to design and optimize the cloak. “By changing the height of each dielectric particle, we were able to control the reflection of light at each point on the cloak,” explains Hsu. “Our computer simulations show how our cloaking device would behave in reality. We were able to reveal that a thin cloak designed with cylinder-shaped dielectric particles can help us significantly reduce the object’s shadow.”
“Doing whatever we want with light waves is really electrifying,” says Kanté. “Using this technology, we can do more than make things invisible. We can change the way light waves are being reflected at will and ultimately focus a large area of sunlight onto a solar power tower, like what a solar concentrator does. We also expect this technology to have applications in optics, interior design and art.”
This work was supported by a contribution from the Calit2 Strategic Research Opportunities (CSRO) program at the Qualcomm Institute at UC San Diego.