This is a portion of a cell making up metamaterial. Credit: Stephane Larouche. |
Duke
University engineers believe that continued advances in creating
ever-more exotic and sophisticated man-made materials will greatly
improve their ability to control light at will.
The
burgeoning use of metamaterials in the field of optics does not rely on
the limited set of materials found in nature, but rather man-made
constructs that can be designed to control light’s many properties. This
control is gained by use of metamaterials, which are not so much single
substances but entire man-made structures that can be engineered to
exhibit properties not readily found in nature.
In
their latest series of experiments, the Duke team demonstrated that a
metamaterial construct they developed could create holograms—like the
images seen on credit or bank cards—in the infrared range of light,
something that had not been done before.
The
Duke engineers point out that while this advance was achieved in a
specific wavelength of light, the principles used to design and create
the metamaterial in their experiments should apply in controlling light
in most frequencies.
“In
the past, our ability to create optical devices has been limited by the
properties of natural materials,” said Stéphane Larouche, research
scientist in electrical and computer engineering at Duke’s Pratt School
of Engineering. “Now, with the advent of metamaterials, we can almost do
whatever we want to do with light.
“In
addition to holograms, the approach we developed easily extends to a
broad range of optical devices,” Larouche said. “If realized, full
three-dimensional capabilities open the door to new devices combining a
wide range of properties. Our experiments provide a glimpse of the
opportunities available for advanced optical devices based on
metamaterials that can support quite complex material properties.”
The
results of Larouche’s experiments, which were conducted in the
laboratory of senior researcher David R. Smith, a professor of
electrical and computer engineering, appeared in an advanced online
publication of the journal Nature Materials. The research was supported
by the Army Research Office’s Multidisciplinary University Research
Initiative (MURI).
The
metamaterial device fashioned by the Duke team doesn’t look anything
like a lens, though its ability to control the direction of rays passing
through it surpasses that of a conventional lens. While traditional
lenses are made of clear substances—like glass or plastic—with highly
polished surfaces, the new device looks more like a miniature set of tan
Venetian blinds.
These
metamaterials are constructed on thin slabs of the same material used
to make computer chips. Metal elements are etched upon these slabs to
form a lattice-like pattern. The metal elements can be arranged in
limitless ways, depending on the properties desired.
“There
is unquestionable potential for far more advanced and functional
optical devices if greater control can be obtained over the underlying
materials,” Larouche said. “The ability to design and fabricate the
components of these metamaterial constructs has reached the point where
we can now build even more sophisticated designs.
“We believe that just about any optical device can be made more efficient and effective using these new approaches,” he said.
The other members of the team, all from Duke, were Yu-Ju Tsai, Talmage Tyler and Nan M. Jokerst.
Source: Duke University
