‘Twisted’ light takes a step forward

Posted on 29 Dec 2017 and read 411 times
‘Twisted’ light takes a step forwardScientists have taken an important step towards using ‘twisted’ light as a form of wireless high-capacity data transmission that could make fibre-optics obsolete. In a report published at the end of October in the journal Science Advances, a team of physicists based in the UK, Germany, New Zealand and Canada describes how new research could overcome the current difficulties with using twisted light across open spaces.

Scientists can ‘twist’ photons — individual particles of light — by passing them through a special type of hologram (similar to that on a credit card,) giving them a twist known as ‘optical angular momentum’ (OAM).

While conventional digital communications use photons as ones and zeros to carry information, the number of intertwined twists in the photons allows them to carry additional data — rather like adding letters alongside the ones and zeros. This means that OAM has the potential to create much higher-bandwidth communications technology.

While OAM techniques have already been used to transmit data along cables, transmitting twisted light across open spaces has been much more challenging.

Even simple changes in atmospheric pressure across open spaces can scatter light beams and cause the spin information to be lost. The researchers examined the effects on both the phase and intensity of OAM carrying light over a real link in an urban environment to assess the viability of these modes of quantum information transfer.

Their free space link — in Erlangen, Germany — was 1.6km long and passed over fields and streets (and close to high-rise buildings) to accurately simulate an urban environment and the atmospheric turbulence that can disrupt information transfer.

Martin Lavery, head of the Structured Photonics Research Group at the University of Glasgow, is the lead author on the team’s research paper.

He said: “A working OAM communications system capable of transmitting data wirelessly across free space has the potential to transform on-line access for developing countries, defence systems and cities around the world.

"We are getting ever closer to developing OAM communications that can be deployed in a real urban setting.”

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