UT Austin engineers publish plans for an invisibility cloak

PotterYou might think that invisibility cloaks belong to the realm of fantasy and comic books. Not so, for researchers at the University of Texas at Austin’s Cockrell School of Engineering.

Recent Paper Outlines New Invisibility Design

According to recent reports from the Cockrell School, faculty members have completed plans for the first ever battery-powered invisibility cloak. Andrea Alù is an associate professor in the Department of Electrical and Computer Engineering and heads the team that has developed the proposal.

Alù’s team’s paper is entitled “Broadening the Cloaking Bandwidth with Non-Foster Metasurfaces” and was published earlier this month in Physical Review Letters. Besides camouflaging, the proposed cloak will have applications ranging from biomedical sensing to radio and cellular communications.

Alù’s paper was co-authored by Christos Argyropoulos, a post-doctoral research fellow, and Pai-Yen Chen, a researcher. All three authors were affiliated with UT Austin at the time of the research.

Benefit of New Cloak Stems from Battery Power

It might be news to most of us that scientists have been developing invisibility cloaks for years. But what is novel about Alù’s research is not merely its subject, but that the proposed cloak is battery-powered. No cloak has yet been presented that is designed to take energy from an outside source.

Thus far, invisibility cloaks have been powered by what is called “passive technology.” Simply put, they are made of materials that reflect light in such a way as to make an object less visible. While so-called “passive cloaks” have been effective, the proposed “active cloaks” would theoretically work even better.

The new invisibility cloaks would function in a much different way from previous designs. Both passive and active cloaks reduce visibility by suppressing the scattering of light that reflects from an object. However, the new designs employ a battery to reduce scattering over a broader range of wavelengths. Besides yielding greater invisibility, the new design also yields a thinner and less bulky cloak.

Some of this research was presented in an earlier paper written by Alù and graduate student, Grancesco Monticone, and published in October’s Physical Review X. The thrust of this earlier paper was that the old invisibility cloaks were limited by their design. Alù and his team sought to prove that passive cloaks would not work at certain frequencies.

For example, an old invisibility cloak might render its cloaked object’s movements visible under white light, according to Alù. This is due to a design flaw shared by all passive cloaks.

However, an active cloak, as outlined by Alù and his team, works around this old design flaw. The addition of batteries and amplifiers would increase the range of frequencies over which the cloak would be effective.

Invisibility Technology has Broad Applications

By now, you might be wondering what all this work might be for, besides gratifying the dreams of eight-year-olds. In fact, the technology Alù and his team are working on might improve wireless communications. Just as invisibility cloaks suppress the waves that allow us to see, they might also suppress waves that interfere with our communications. And UT Austin researchers are at the center of this exciting new research.