Today, our international internet links are bedevilled by unavoidable lag - the time it takes for data to travel from the US to a user's PC in Australia. For most of its journey, the data travels at the speed of light along optical fibres. But each time the information stream is switched, amplified, reprocessed or regenerated, it requires silicon-based electronics, which are much slower.

These bottlenecks stand in the way of a 1000-fold increase in the practical speed of the internet, the centre's researchers say. But they could be removed with optical computing, which uses light to switch light, without electronic interference. Research director Ben Eggleton says the centre's program has four strands: a "regenerator" that reproduces an optical signal without electronics; a switch that uses a light signal to direct another light signal; optical buffers to slow light pulses, making them easier to handle; and three-dimensional photonic circuits. The centre's participants at Sydney University and the Australian National University are about a month away from demonstrating an optical switch, he says. (The centre's other members are Macquarie University, University of Technology Sydney, and Swinburne University of Technology.)

Although scientists around the world work on the same problem, Professor Eggleton says the centre takes a unique approach. It is working with a soft glass called chalcogenide, which changes its refracting properties when hit by high-intensity pulses of light - becoming a basic switch. The glass switches at very low powers, which makes it easier to work with and promises more practical applications.

Chalcogenide can also be printed, to create circuits. Scientists created "band gap" structures within the glass - patterns of tiny holes that further control the light beams. Professor Eggleton says this band gap could be the photonic equivalent of the basic unit of electronics - the semi-conductor. "The band gap allows light to be moved in a particular direction. It allows us to make circuitry," he says. "So we have a very compact, low-power optical switch that can be incorporated into an optical circuit, which can be made using basic lithography (circuit printing)." Other optical switches have been demonstrated using silicon, but the use of glass should allow much higher speeds.

The team hopes to demonstrate its first optical switch within the next few months. This would be an early step in creating a practical photonic circuit. Such a circuit would dramatically improve the speed of data-flow around the world.

"The aim is to do more and more signal processing optically," Professor Eggleton says. A beam of light is much faster and more agile than an electronic current. "Electronics relies on electrons moving through semi-conducters and that has a real, inherent speed limit," Professor Eggleton says. "Photonics could be used in telecommunications or even in computing technology."

THE PHOTONIC CHIP 1 Optical data signals (light pulses) enter the chip via glass fibres thinner than a human hair. They are squeezed to fit the optical circuitry.

2 A switch, controlled by light, rapidly combines packets of optical data. 3 Integrated components act on the light, for instance changing its colour from blue to red, amplifying or delaying the signals. 4 The prism-like structure allows some colour data channels to be dropped while other channels are added for the next leg of the trip.

SOURCE: CUDOS, USYD