Novel approach to squeeze light may open doors for optical communications

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London, July 31 : Scientists at the University of California, Berkeley, claim to have discovered a technique that can help squeeze light into tighter spaces than ever thought possible.

The researchers say that their work may open the door to new technology in the fields of optical communications, miniature lasers, and optical computers.

Xiang Zhang, a professor of Mechanical Engineering who led the study, says that the new technique can confine light in incredibly small spaces on the order of 10 nanometres, only five times the width of a single piece of DNA and more than 100 times thinner than current optical fibres.

"This technique could give us remarkable control over light, and that would spell out amazing things for the future in terms of what we could do with that light," Nature Photonics quoted Rupert Oulton, research associate in Zhang's group and lead author of the study, as saying.

Zhang highlighted the fact that just as computer engineers cram more and more transistors into computer chips in the pursuit of faster and smaller machines, researchers in the field of optics have been looking for ways to compress light into smaller wires for better optical communications.

"There has been a lot of interest in scaling down optical devices. It's the holy grail for the future of communications," Zhang said.

Scientists hope that compressed light could make possible smaller optical fibres, and lead to huge advances in the field of optical computing.

Oulton said that many researchers want to link electronics and optics, but light and matter make strange bedfellows because their characteristic sizes are on vastly different scales.

The researcher, however, agrees that confining light could actually alter the fundamental interaction between light and matter, and that optics researchers would like to cram light down to the size of electron wavelengths to force light and matter to cooperate.

The researchers have revealed that could squish light beyond its wavelength using surface plasmonics, where light binds to electrons allowing it to propagate along the surface of metal.

Using computer simulations, they discovered that not only could the light compress into spaces only tens of nanometres wide, but it could travel distances nearly 100 times greater in the simulation than by conventional surface plasmonics alone.

Instead of the light moving down the centre of the thin wire, as the wire approaches the metal sheet, light waves are trapped in the gap between them, the researchers found.

Oulton said that the new approach worked because the hybrid system acts like a capacitor, storing energy between the wire and the metal sheet.

"Previously, if you wanted to transmit light at a smaller scale, you would lose a lot of energy along the path. To retain more energy, you'd have to make the scale bigger. These two things always went against each other. Now, this work shows there is the possibility to gain both of them," Zhang said.

Oulton said that, even though the current study is theoretical, the construction of such a device should be straightforward.

According to the researcher, the problem lies in trying to directly detect the light in such a small space - no current tools are sensitive enough to see such a small point of light.

Zhang's group, meanwhile, is looking for other ways to experimentally detect the tiny bits of light in these devices.

Oulton believes that the hybrid technique of confining light could have huge ramifications, and that it may be an important step on the road to an optical computer, a machine where all electronics are replaced with optical parts.

The construction of a compact optical transistor is currently a major stumbling block in the progress toward fully optical computing, and this technique for compacting light and linking plasmonics with semiconductors might help clear this hurdle, the researchers said.

ANI

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