[ASC-media] The perfect slow wave

Niall Byrne niall at scienceinpublic.com.au
Mon Oct 23 00:16:22 CEST 2006

The perfect slow wave

23 October 2006

Sydney physicists have invented a device that creates perfect slow light
waves. Their discovery, reported today in Nature Physics, brings
light-based computing and communications a step closer and uses a
discovery first made in a Scottish ship canal over 170 years ago. 

Their device slows light by about 20 percent without losing information.
Until now, when light was slowed down information was lost. But the self
reinforcing soliton waves made by the device ensure that the shape of
the wave is maintained. 

This matters because communications depend on buffering - holding and
releasing batches of information. In this experiment the team buffered
just a few bits. If they can get to 100 bits then the team from CUDOS, a
consortium of five universities will have a winner. 

These slow waves could help unleash a much faster internet, and replace
the millions of energy hungry routers that power the web. "We are
planning to work with Australian companies to bring the technology to
market," says Professor Ben Eggleton, leader of the research team. 

In 1834, a Scottish engineer was observing a boat being pulled along a
canal. The boat stopped, and a mass of water built up in front of it.
The water then rolled forward, leaving the boat behind, and continued,
as a solitary wave, 30 feet long and one to one-and-a-half feet high
travelling for miles without breaking up. The shape of the canal was
such that it created a 'self-reinforcing single wave'.

Similar waves in nature include tidal bores like the Severn Bore, and
the atmospheric waves that cause Morning Glory clouds in Queensland.
Normal waves would break down, flatten out, topple over or crumble after
a short distance. But solitons keep going, whether they're made of water
or light. But what's the connection with the internet? 

"The net comprises a web of fibre optic cables carrying vast amounts of
information as light. But the routers and switchers that direct the
traffic are electronic," says Professor Ben Eggleton, leader of the
research team. 

"They're a bottleneck, and they are consuming vast amounts of energy
both directly and indirectly through the banks of air conditioners
required to keep them cool," 

"The dream of photonics is to replace all that slow electronics with
light. So the challenge is to create analogues of all the electronic
components - transistors, capacitors, buffers etc. And the ability to
slow light is critical for buffering information. But until now, the
slow light devices had limited bandwidth - and as the light waves slowed
they were also damaged, destroying the information they were carrying,"
says Ben. 

"We found that by passing the light pulses through a glass that reacts
more strongly to brighter light, we could get the wave to reinforce
itself - making a soliton, a single wave that will travel as far as
needed without distortion.

The light is guided through a carefully designed crystal lattice within
a five cm piece of optical fibre.

"We anticipate that we will be able use fibres that are tens of
centimetres long (but curled up within an integrated device and
ultimately part of a photonic integrated circuit -- the photonic chip),
allowing us to slow the light to order. We have also shown that we can
tune the fibre - controlling the speed of the pulses as they travel
through the fibre," says Ben Eggleton. 

"We believe we can turn this early fundamental discovery into a
practical device that will bring ultra-fast internet - and opportunities
for Australian companies to jump on the next wave of the internet
revolution," says Ben. 

CUDOS is the Centre for Ultrahigh Bandwidth Devices for Optical Systems.
It is a consortium between five Australian Universities: The University
of Sydney, Macquarie University, University of Technology Sydney,
Australian National University and Swinburne University of Technology. 

Funding comes from the Australian Research Council under the Centres of
Excellence program, the five universities and from the NSW State

For interviews: Ben Eggleton,  +61 (2) 9351 3604, 0413 385 715,
egg at physics.usyd.edu.au, Chris Walsh, +61 (2) 9351 5897, 0401 05 5494,


Niall Byrne
Science in Public
Ph +61 3 5253 1391
niall at scienceinpublic.com
OR niallprivate at scienceinpublic.com
PO Box 199, Drysdale Vic Australia

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