[Nfb-science] No Magic: Invisibility Cloak Gets a Step Closer

[Jewel S.]

No magic: Invisibility cloak gets a step closer
from the Raleigh News & Observer, March 19, 2010

>From Grimm's fairy tales to Harry Potter, the cloak of invisibility
has played a major role in fiction. Now scientists have taken a small
but important new step toward making it reality. Researchers at
Germany's Karlsruhe Institute of Technology report 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 -
that bends light, hiding the bump in the gold layer beneath, the
researchers reported recently in the online edition of the journal
Science. In this case, the bump was tiny, a mere 0.00004 inch high and
0.0005 inch across, so that a magnifying lens was needed to see it. In
principle, the cloak design is completely scalable; there is no limit
to it," Ergin said. But, he added, developing a cloak to hide
something takes a long time, "so cloaking larger items with that
technology is not really feasible. Other fabrication techniques,
though, might lead to larger cloaks," he added in an interview via
e-mail. The value of the finding, Ergin said, "is that we learn more
about the concepts of transformation optics and that we have made a
first step in producing 3-D structures in that field. 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. In earlier research, a team led by David Schering at Duke
University developed a way to cloak objects in two dimensions from
microwaves. Like light and radar waves, microwaves usually bounce off
objects, making them visible to instruments and creating a shadow that
can be detected. The new research led by Ergin used infrared waves,
which are close to the spectrum of visible light. 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.
Ergin's research was supported by the German Research Council, the
state of Baden-Wuerttemberg, the European Commission and the German
Ministry for Education and Research. On the Net:  www.sciencemag.org .