By Roland Piquepaille
It's not the first time that physicists claim that the speed of light can be modified, and even exceed the theoretical limit called c without violating Einstein's laws of relativity (check for example this article from two years ago). Now, researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Lausanne, Switzerland, claim that light can travel faster than light!. They were able to control the speed of light in an off-the-shelf optical fiber. They said that they did "slow a light signal down by a factor of 3.6 (or about 71,000 km/s), creating a sort of temporary "optical memory." On the other hand, they also did create "extreme conditions in which the light signal travelled faster than 300 million meters a second." As they don't give any numbers for this upper limit, you have to trust them. Anyway, these results are important because they were achieved using off-the-shelf optical fibers, opening the way for future super fast all-optical routers. Update (August 22, 2005): Luc Thévenaz sent me insightful comments about this post. You'll find them at the end of this entry.So what have done Luc Thévenaz and his fellow researchers in the EPFL's Nanophotonics and Metrology laboratory (page in French)?
The telecommunications industry transmits vast quantities of data via fiber optics. Light signals race down the information superhighway at about 186,000 miles per second. But information cannot be processed at this speed, because with current technology light signals cannot be stored, routed or processed without first being transformed into electrical signals, which work much more slowly. 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.
This is exactly what the EPFL team has demonstrated. Using their Stimulated Brillouin Scattering (SBS) method, the group was able to slow a light signal down by a factor of 3.6, creating a sort of temporary"optical memory." They were also able to create extreme conditions in which the light signal travelled faster than 300 million meters a second. And even though this seems to violate all sorts of cherished physical assumptions, Einstein needn't move over
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