at a wide range of light frequencies.
But, unfortunately for Harry Potter fans, they are still a long way
off making objects disappear completely.
In fact, they admitted that certain frequencies make the objects MORE
visible in their study, published in the journal Physical Review X.
But the group have invented what they believe to be the next best
thing – a broadband 'cloak', based on an electronic system, which they
describe in Physical Review Letters.
Professor Andrea Alu, from the University of Texas at Austin, told the
BBC: "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."
He added: "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."
And much more than just a childhood dream, this invention could have
huge uses in microscopy, military technology and biomedical sensing,
according to the study.
But while the object may be invisible at one point in the light
spectrum, it acts as a sort of beacon at another point – so it can
never be completely invisible.
The scientific study concluded that a fully functioning invisibility
cloak is "impossible".
Professor Alu told the BBC: "If you suppress scattering in one range,
you need to pay the price, with interest, in some other range."
He added: "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."
It's not the first attempt at such a design.
Professor David Smith of Duke University made the first cloak in 2006,
which bent microwaves around a small copper cylinder.
He told the BBC: "It's an interesting implementation but as presented
is probably a bit limited to certain types of objects."
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