[August 14, 2008]

UC-Berkeley: Invisibility cloak moves from fantasy to potential reality at UC Berkeley

(U-Wire Via Acquire Media NewsEdge)
UWIRE-08/14/2008-UC-Berkeley: Invisibility cloak moves from fantasy to
potential reality at UC Berkeley (C) 2008 Daily Californian via UWIRE

By Hadas Goshen, Daily Californian (UC-Berkeley)

BERKELEY, Calif. --

Whispers of a potential invisibility cloak are floating among the labs
of Univeristy of California Berkeley researchers, and contrary to
notions of fact and fantasy, these are not the ravings of mad
scientists.

Recent breakthroughs at campus labs have left scientists considering
the possibility of designing cloaking devices that make objects
invisible to human sight. They have already engineered remarkable
composite materials known as "metamaterials" capable of reversing the
natural direction of visible and near-infrared light.

The benefits of such materials are numerous, and according to the
project's research manager Guy Bartal, the labs' two main projects are
milestones for the future of light-bending research. UC Berkeley
researcher Thomas Zentgraf said he believes the studies will expand
scientific possibilities, making way for new designs for optical lenses
or optical computers.

"As a result of a lens or microscope objective made of such a material,
we would be able to get better images with much higher resolution than
those possible today," Zentgraf said. "This would be very interesting
for biological applications to observe living viruses or DNA directly
in a normal microscope."

But the most popular discussion for the future of negative index
materials remains largely on the development of cloaking devices, made
possible by the metamaterials' ability to guide light around an object
without disturbing the light after it passes.

"An observer would not recognize that there is an object between them
and the source where the light comes from, making the object optically
invisible," Zentgraf said. "Of course this sounds like science fiction,
and we are still far away from doing this for visible light, but
nevertheless our work is one step in this direction."

While Zentgraf maintains that cloaking devices are a long way away, UC
Berkeley's metamaterials research has sparked the interest of the U.S.
government, particularly the military.

In addition to funding from the National Science Foundation, the U.S.
Army Research Office has given support to one of the lab's projects and

the U.S. Air Force Office of Scientific Research has aided the other.
Bartal says this is "not surprising," and should researchers eventually
design a cloaking device, there will be military uses for it.

The grants have enabled scientists to use specially-designed
nanotechnology, creating metamaterials with a negative refraction index
which, unlike naturally occurring materials, enables them to bend light
backwards.

"The basics of this phenomenon lies in the basics of metamaterials,"
said Bartal. "Using nanotechnology, we were able to design these
materials comprised of very tiny elements, and when light goes through
them they respond with properties that do not exist in nature, unlike
glass or water or crystals that bend light naturally."

In one such case, campus researchers constructed a type of "fishnet"
comprised of alternating layers of silver and non-conducting magnesium
fluoride, achieving a negative refraction of light, with both
electrical and magnetic fields in the light wave moving backward in the
material.

While it seems invisibility cloaks are no longer confined to the world
of J.K. Rowling, it's unlikely that such a product will ever be
developed for mass manufacturing. The techniques used for the
fabrication of lab samples was limited to small sizes, and the unique
bending of light is difficult to achieve.

But with future improvements of nanofabrication techniques, Zentgraf
says he is optimistic that he and his team will continue to build
substantial devices out of such metamaterials.

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