_Invisibility Undone: Chinese Scientists Demonstrate How To_
(http://www.photonic<WBR>sonline.com/<WBR>article.mvc/<WBR>Invisibility-<WBR>Undone-Chinese-<WBR>Scientists-<WBR>0001)

So are those "blinking" out UFO's coated with meta material ..... mmmm - crg

* "...All materials scatter, bounce, absorb, reflect and otherwise
alter light rays that strike them. We perceive color, for instance, because
different materials and coatings interact with light differently.
* Transformation media cloaks are special materials that can bend
light so much that it actually passes around the object completely. In 2006,
scientists at Duke University demonstrated in the laboratory that an object made
of metamaterial is partially invisible when viewed using microwaves. ..."
* [an] "...."anti-cloak" would be a material with optical properties
perfectly matched to those of an invisibility cloak. (In technical jargon, an
anti-cloak would be anisotropic negative refractive index material that is
impedance matched to the positive refractive index of the invisibility cloak).
* While an invisibility cloak would bend light around an object, any
region that came into contact with the anti-cloak would guide some light back
so that it became visible.
* This would allow an invisible observer to see the outside by
pressing a layer of anti-cloak material in contact with an invisibility cloak. ..."


Invisibility Undone: Chinese Scientists Demonstrate How To Uncloak An
Invisible Object

September 5, 2008

Washington, DC - Harry Potter beware! A team of Chinese scientists has
developed a way to unmask your invisibility cloak. According to a new paper in the
latest issue of Optics Express, the Optical Society's (OSA) open-access
journal, certain materials underneath an invisibility cloak would allow invisible
objects be seen again.
"Cloaking is an important problem since invisibility can help survival in
hostile environment,<WBR>" says Huanyang Chen of Shanghai Jiao Tong University in
China. He and his colleagues have proposed a theoretical "anti-cloak" that
would partially cancel the effect of the invisibility cloak, which is another
important problem as it turns out.
If this sounds like more movie magic, it's no accident. From the 1933
classic The Invisible Man to the more recent installment in the Harry Potter
series, devices that achieve invisibility have long been the stuff of film fantasy.
In recent years, however, scientists using special types of "meta" materials
have shown that these Hollywood fantasies could one day become reality after
all.
These materials are effectively invisible because of the way they interact
with light. All materials scatter, bounce, absorb, reflect and otherwise alter
light rays that strike them. We perceive color, for instance, because
different materials and coatings interact with light differently. Transformation
media cloaks are special materials that can bend light so much that it actually
passes around the object completely. In 2006, scientists at Duke University
demonstrated in the laboratory that an object made of metamaterial is
partially invisible when viewed using microwaves.
Sounds cool? Not so fast. Invisibility as it has been achieved so far in the
laboratory is very limited. It works, but only for a narrow band of light
wavelengths. Nobody has found a way yet to make an object invisible to the
broad range of wavelengths our eyes are attuned to seeing, says Chen, and doing
so would be a challenge.
An even greater problem for anyone who has aspirations to be concealed in
public one day is that invisibility achieved through transformation media is a
two-way street. With no light penetrating a perfect invisibility cloak, there
would be no way for an invisible person to see outside. In other words,
invisible people would also be blindnot exactly what Harry Potter had in mind.
But now, Chen and his colleagues have developed way to partially cancel the
invisibility cloak's cloaking effect. Their "anti-cloak" would be a material
with optical properties perfectly matched to those of an invisibility cloak.
(In technical jargon, an anti-cloak would be anisotropic negative refractive
index material that is impedance matched to the positive refractive index of
the invisibility cloak).
While an invisibility cloak would bend light around an object, any region
that came into contact with the anti-cloak would guide some light back so that
it became visible. This would allow an invisible observer to see the outside
by pressing a layer of anti-cloak material in contact with an invisibility
cloak.
"With the anti-cloak, Potter can see outside if he wants to," says Chen, who
conducted the research together with his colleagues at Shanghai Jiao Tong
University and The Hong Kong University of Science and Technology.
SOURCE: American Institute of Physics