14 DAY TRIAL // Conventional lenses, no matter how powerful, are only able to magnify light to nearly half of the wavelength, or the so-called diffraction limit. This basically means that the dimensions of optical storing devices or the sizes of the features created on silicon chips are limited to how much focusing power a particular lens has. By implying the use of metamaterials, the researchers at the University of Michigan claim that they will soon be able to create a superlens capable of focusing ten times more light than a conventional lens.
Because metamaterials have negative refraction indexes, they may be able to create lenses that surpass the diffraction limitation of conventional optical lenses. Metamaterials have previously been presented as a possible material for the construction of invisibility, acoustic and even magnetic cloaks. Metamaterials are created out of intricate metal structures able to bend waves through their mass in unique ways.
Metamaterials
The metamaterial superlens was predicted last year by Anthony Grbic, Lei Jiang and Roberto Merlin from the University of Michigan, and was recently build out of a plate of teflon and ceramic with a copper topping, only 127 micrometer-thick. "The beauty of these is that they're planar and easy to fabricate," says Grbic.
It was built through an etching process, very similar to that used to produce computer chips, on a copper plate. Selective etching created multiple capacitors sitting on top of each other, which are able to interact with electromagnetic waves - capacitors, are electronic devices capable of storing electric energy for short amounts of time.
The interaction between the capacitors and the passing electromagnetic waves determines an electric current inside the capacitors, thus focusing the waves into a point 20 times smaller that the wavelength of light. This basically means that the new superlens is at least ten times more powerful than a conventional lens.
Limitations
For now, the device works only in the microwave wavelengths. Similarly to the case of the electromagnetic cloak, the lens' frequency range is limited by the size of the capacitors. By making them of different sizes, the metamaterial superlens would be able to focus all the frequencies in the visible or infrared light.
It would become extremely useful in the etching process on computer chips, optical storing devices and even wireless power transfer.
"This is an important step forward in sub-wavelength imaging with considerable potential applications," said John Pendry of the Imperial College London, one of the first scientist that used metamaterials to prove that electromagnetic cloaks could be possible. Nader Engheta of the University of Pennsylvania reckons that by making metamaterials more complex, they would have even more possible applications.