Simple 'superlens' sharpens focusing power - tech - 24 April 2008
- New Scientist Tech
ACCESSED: Thu Apr 24 2008 14:30:03 GMT-0400 (EDT)
PAGE URL: http://technology.newscientist.com/article/dn13771
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Simple 'superlens' sharpens focusing power
* 19:00 24 April 2008
* NewScientist.com news service
* Mason Inman
A simple-to-make "superlens" can focus 10 times more sharply
than a conventional lens. It could shrink the size of features on
computer chips, or help power gadgets without wires.
No matter how powerful a conventional lens, it cannot focus
light down to more than about half its wavelength, the
"diffraction limit". This limits the amount of data that can be
stored on a CD, and the size of features on computer chips.
Researchers have devised ways to beat the diffraction limit
before, using bizarre "metamaterials" that are hard to make, and
which are also the basis of prototype "invisibility cloaks".
But such complex mixes of material stuffed with tiny loops of
metal and precisely-shaped holes are unlikely to become a mass-
production technology.
Anthony Grbic, Lei Jiang and Roberto Merlin at the University of
Michigan in Ann Arbor, US, have now successfully made a much
simpler design, first theorised last year.
The new lens is a 127-micrometer-thick plate of teflon and
ceramic with a copper topping. "The beauty of these is that
they're planar," Grbic says, "they're easy to fabricate." The lenses
can be made through a single step of photolithography, the
process used to etch computer chips.
By selectively etching away the copper, Grbic and colleagues
created many capacitors sandwiched together. Capacitors are
typically used in electronics for storing electric charge for short
periods.
In the lens, the capacitors instead interact directly with
electromagnetic waves like light. This sets up currents in the
capacitors that focus the waves passing through the lens into a
point 20 times smaller than their wavelength. That is 10 times
tighter than a conventional lens can achieve, hampered by the
diffraction limit. Microwave trials
The team's current prototype works on microwaves, which are
easier to focus because they have longer wavelengths than visible
light. Simply making capacitors of different sizes would allow the
lens to focus other frequencies, including visible and infrared
light, says Grbic.
Grbic and colleagues have a variety of uses for their new lenses
planned, including focusing light into smaller spots during
photolithography to etch smaller features onto computer chips.
The lenses could also help refine a technique to transfer power
wirelessly developed in 2006. The new lenses could create more
energy-dense beams of the electromagnetic waves used to
transfer power, Grbic says. "Ingenious"
The theory behind these lenses is "ingenious," says John Pendry
of Imperial College London, UK, who in 2006 proved invisibility
cloaks could be possible. "This is an important step forward in
sub-wavelength imaging with considerable potential
applications," he adds.
Nader Engheta of the University of Pennsylvania in Philadelphia,
US, agrees, saying the new design has "exciting potential." But
the more complex metamaterial lenses will likely be more
applicable to more diverse applications, he adds.
Journal reference: Science (DOI: 10.1126/science.1154753)
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