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Photonic chips turn lightning into thunder


Converting data from light to sound can give optical computers the time to think, writes Andrew Masterson.


The chalcogenide glass chip next to an Australian 50-cent piece for scale.
The chalcogenide glass chip next to an Australian 50-cent piece for scale.
University of Sydney

How do you slow down lightning? Turn it into thunder.

Researchers at Australia’s Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS) at the University of Sydney have done just that, albeit in a rather more strictly defined and managed sense. In doing so, they have potentially solved a couple of major issues handicapping the fast-growing cloud computing and telecommunications industries.

A team of researchers led by Moritz Marklein and Birgit Still has successfully stored information on a microchip by converting data encoded in light into sound.

The world-first achievement is reported a paper published in the journal Nature Communications.

A stylised animation of the operation of the chip.
How the chip works. A data pulse of light (yellow) enters the chip from the left and meets another pulse (blue) from the right. They interact and produce an acoustic wave that stores the information from the data pulse. Another blue pulse enters and interacts with the acoustic wave to transmit a data pulse (yellow) to the right.
Rhys Holland & Sebastian Zentilomo / University of Sydney

The acoustic data is stored for only a brief period before being turned once again into light and sent on its way. The interval, however, is extremely valuable: it enables sufficient time for the information to be processed and distributed.

Doing this using current communications technology requires using electronics, a process that generates heat. In a single circuit the heat generated is negligible, but when circuits are combined and scaled up to the size of a telecommunications or cloud computing system the thermal output is sizeable and costly.

Electronic systems are also vulnerable to electromagnetic interference.

Recognising this, tech giants such as IBM have been working on the development of photonic chips – microprocessors that use light instead of electricity, seen as a critical step in building quantum computers. These bring a number of advantages – they are very good for sending information over long distances at high speeds through fibre optic cables, and because they use photons rather than electrons they are not prey to the distorting influence of electromagnetism.

However, their speed is also an impediment to accessing the information they contain.

“For this to become a commercial reality, photonic data on the chip needs to be slowed down so that they can be processed, routed, stored and accessed,” explains Merklein.

In order to do that the CUDOS scientists succeeded in building an acoustic buffer inside a chip, which not only slows the incoming information down by converting it to sound, but also allows each chip to store and retrieve information across several wavelengths at the same time.

“The information in our chip in acoustic form travels at a velocity five orders of magnitude slower than in the optical domain,” says Still. “It is like the difference between thunder and lightning.”

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Andrew Masterson is news editor of Cosmos.
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