High-capacity wireless communications using ‘twisted light’ closer to reality
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Researchers based at the University of Glasgow have transmitted ‘twisted’ photons across a mile of turbulent air, identifying some of the difficulties that must be resolved to make this form of data transmission a reality.
Conventional digital communications use photons (individual packets of light) to carry data in a sequence of zeroes and ones. Adding spin information to these photons could allow for an enormous amount of additional information to be carried in each particle, much like adding the alphabet to the zeroes and ones.
This extra information can be added to the photons using a particular type of hologram to ‘twist’ them, giving them optical angular momentum.
While this has already been proved possible in studies using cables to transmit the photons, the true potential of twisting photons to store information is in wireless, high-capacity data transmission. This could allow for far higher bandwidth communication, and could make fibre-optics obsolete.
“In an age where our global data consumption is growing at an exponential rate, there is mounting pressure to discover new methods of information-carrying that can keep up with the huge uptake in data across the world,” said Dr Martin Lavery, head of the Structured Photonics Group at the University of Glasgow, and lead author of the Science Advances study.
“Free space optics is a solution that can potentially give us the bandwidth of fibre, but without the requirement for physical cabling.”
In order for this technology to be commercially viable, it must be possible to transmit data wirelessly and securely. This is particularly challenging due to the smallest changes in atmospheric pressure causing photons to be scattered and information to be lost.
Dr Lavery and his colleagues transmitted twisted photons across an open air space of 1.6km (1 mile). This environment was full of high-rise buildings, streets and fields, with ordinary atmospheric turbulence. They used this to study how phase and intensity of optical angular momentum is affected in these chaotic environments.
The researchers were able to identify previously unnoticed challenges – including rethinking approaches to channel modelling – which must be resolved to make adaptive optical systems a commercial reality.
“This study takes vital steps forward in the journey towards high-dimensional free space optics that can be a cheaper, more accessible alternative to buried fibre optics connections,” said Dr Lavery.
“A complete, working optical angular momentum communications system capable of transmitting data wirelessly across free space has the potential to transform online access for developing countries, defence systems and cities around the world.”