Wireless Power and the Superlens

The superlens will open up new options for wireless power like this experiment conducted at MIT

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.
Simply super

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.

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.

Via New Scientist