No one has yet made a superlens, also known as a perfect lens, though
people are trying. Optical lenses are limited by the nature of light,
the so-called diffraction limit, so even the best won't usually let us
see objects smaller than 200 nanometers across, about the size of the
smallest bacterium. Scanning electron microscopes can capture objects
that are much smaller, about a nanometer wide, but they are expensive,
heavy, and, at the size of a large desk, not very portable.
In this illustration of Durdu Guney's theoretical metamaterial, the
colors show magnetic fields generated by plasmons. The black arrows show
the direction of electrical current in metallic layers, and the numbers
indicate current loops that contribute to negative refraction.
To build a superlens, you need metamaterials: artificial materials
with properties not seen in nature. Scientists are beginning to
fabricate metamaterials in their quest to make real seemingly magical
phenomena like invisibility cloaks, quantum levitation -- and
superlenses.
Now Guney, an assistant professor of electrical and computer
engineering at Michigan Technological University, has taken a major step
toward creating superlens that could use visible light to see objects
as small as 100 nanometers across.
The secret lies in plasmons, charge oscillations near the surface of
thin metal films that combine with special nanostructures. When excited
by an electromagnetic field, they gather light waves from an object and
refract it in a way not seen in nature called negative refraction. This
lets the lens overcomes the diffraction limit. And, in the case of
Guney's model, it could allow us to see objects smaller than 1/1,000th the width of a human hair.
Other researchers have also been able to sidestep the diffraction
limit, but not throughout the entire spectrum of visible light. Guney's
model showed how metamaterials might be "stretched" to refract light
waves from the infrared all the way past visible light and into the
ultraviolet spectrum.
Making these superlenses would be relatively inexpensive, which is
why they might find their way into cell phones. But there would be other
uses as well, says Guney.
"It could also be applied to lithography," the microfabrication
process used in electronics manufacturing. "The lens determines the
feature size you can make, and by replacing an old lens with this
superlens, you could make smaller features at a lower cost. You could
make devices as small as you like."
Computer chips are made using UV lasers, which are expensive and
difficult to build. "With this superlens, you could use a red laser,
like the pointers everyone uses, and have simple, cheap machines, just
by changing the lens."
What excites Guney the most, however, is that a cheap, accessible
superlens could open our collective eyes to worlds previously known only
to a very few.
"The public's access to high-powered microscopes is negligible," he
says. "With superlenses, everybody could be a scientist. People could
put their cells on Facebook. It might just inspire society's scientific
soul."
Guney and graduate student Muhammad Aslam published an article on
their work, "Surface Plasmon Diven Scalable Low-Loss Negative-Index
Metamaterial in the visible spectrum," in Physical Review B, volume 84,
issue 19.0
From sciencedaily
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