Swiss scientists break the cosmic speed limits of light

September 2, 2005

Brussels, 01 Sep 2005

An international team of researchers at the École Polytechnique Fédérale de Lausanne (EPFL), Switzerland, has succeeded in controlling the speed of light in optical fibres using simple off-the-shelf instrumentation, in normal environmental conditions. The discovery could have applications ranging from optical computing to the fibre-optic telecommunications industry.

In recent times, scientists have succeeded in doing all sorts of things with light, including slowing it down and even stopping it all together. The enormous advantage of the EPFL team's new method is that special media such as cold gases or crystalline solids are not needed. Moreover, the method works at any wavelength, unlike previous techniques. They are also able to tune the speed of the light signal, thus achieving a wide range of delays.

'This has the enormous advantage of being a simple, inexpensive procedure that works at any wavelength, notably at wavelengths used in telecommunications,' explains lead researcher Luc Thévenaz.

Optical fibres cross cities and oceans, transmitting vast quantities of data through the world's high-speed data communications network. But the throughput of optical fibre is limited by how fast data can be switched across networks. Light signals race down the information superhighway at about 300,000 kilometres per second.

But information cannot be processed at this speed as current technology cannot store light signals, route or process them, without first being transformed into electrical signals, which work much more slowly. In a conventional router, light from fibres must be converted into an electrical signal, switched to an appropriate cable, then converted back to light again. This process can slow the speed of information transfer by a factor of ten. A router that did not need to use an electrical signal would be inherently faster. If the light signal could be controlled by light, it would be possible to route and process optical data without the costly electrical conversion, opening up the possibility of processing information at the speed of light.

The EPFL team has brought applications of slow light an important step closer to this. Using a technique called Stimulated Brillouin Scattering, the researchers were able not only to slow light down by a factor of three from its well established speed of 300 million meters per second in a vacuum. They have also succeeded in speeding it up - making light go faster than the speed of light.

Dr Thévenaz points out that this technology could take them far beyond just improving current telecom applications. He suggests that their method could be used to generate high-performance microwave signals that could be used in next-generation wireless communication networks, or used to improve transmissions between satellites. To download an abstract of research paper, please: click here

Remarks: Reference document: Optically controlled slow and fast light in optical fibres using stimulated Brillouin scattering. Miguel González-Herráez, Kwang-Yong Song, and Luc Thévenaz. Appl. Phys. Lett. 87, 081113 (22 August 2005)

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