Scientists reveal breakthrough on ‘invisibility cloak’

FROM Grimms’ fairy tales to Harry Potter, the cloak of invisibility has played a major role in fiction.

Now scientists have taken a small but important step towards making it a reality.

Researchers at Germany’s Karlsruhe Institute of Technology report that they were able to cloak a tiny bump in a layer of gold, preventing its detection at nearly visible infrared frequencies.

Their cloaking device also worked in three dimensions, while previously developed cloaks worked in two dimensions, lead researcher Tolga Ergin said.

The cloak is a structure of crystals with air spaces in between, sort of like a woodpile, which bends light, hiding the bump in the gold layer beneath, the researchers reported in yesterday’s online edition of the journal Science.

In this case, the bump was tiny, a mere 0.00004in (1 micrometer) high and 0.0005in (13 micrometer) across, so a magnifying lens was needed to see it.

“In principle, the cloak design is completely scalable; there is no limit to it,” Mr Ergin said. But developing a cloak to hide something takes a long time, “so cloaking larger items with that technology is not really feasible”, he added.

“Invisibility cloaks are a beautiful and fascinating benchmark for the field of transformation optics, and it is very seldom that one can foretell what practical applications might arise out of a field of fundamental research,” he added.

In cloaking, special materials deflect radar, light or other waves around an object, like water flowing around a smooth rock in a stream.

It differs from stealth technology, which does not make an aircraft invisible but reduces the cross-section available to radar, making it hard to track.