Scientists have successfully designed an invisibility cloak that can hide matter in various types of frequencies using an extremely thin electronic system.
Prof. Andrea Alu, lead author of the study and an associate professor at the University of Texas, wrote, "Our active cloak is a completely new concept and design, aimed at beating the limits of (current cloaks) and we show that it indeed does.”
The first invisibility cloak was first revealed in 2006. It bended microwaves around a small copper cylinder which allowed it to vanish. Since it releases more radiation, the current models have limitations. The cloaks only hide objects in certain frequencies; in others frequencies, they only act as neon signs. The most recent 3D invisibility cloak launched in 2012 was only capable of concealing matter from microwaves.
The researchers conducted tests on three common types of “passive” models of non-electric invisibility cloaks: the plasmonic cloak, the mantle cloak, and the transformation-optics cloak. When they tried to apply electromagnetic waves on them, they found that they radiated more waves than a non-cloaked object. Thus, they believe that complete invisibility is not possible using current designs.
"If you suppress scattering in one range, you need to pay the price, with interest, in some other range. For example, you might make a cloak that makes an object invisible to red light. But if you were illuminated by white light (containing all colours) you would actually look bright blue, and therefore stand out more,” Prof. Alu explained to BBC.
The scientists designed an active cloaking technology, one that conceals using electrical power that renders matter invisible through amplifiers that cover the object’s exterior with electric current.
"If you want to make an object transparent at all angles and over broad bandwidths, this is a good solution. We are looking into realising this technology at the moment, but we are still at the early stages," Prof. Alu said.
Some of the significant applications of this cloaking technology is in telecommunications, microscopy, military, energy-harvesting devices, and biomedical sensing. One example is a cloak that uses radio frequency that may make wireless communications more effective: it could circumvent and decrease interferences from nearby antennae.
The study was published in the Nov. 12 issue of the Physical Review Letters.
