Slow light
Slow light is the propagation of an optical pulse or other modulation of an optical carrier at a very low group velocity. Slow light occurs when a propagating pulse is substantially slowed down by the interaction with the medium in which the propagation takes place.
In 1998, Danish physicist Lene Vestergaard Hau led a combined team from Harvard University and the Rowland Institute for Science which succeeded in slowing a beam of light to about 17 meters per second, and researchers at UC Berkeley slowed the speed of light traveling through a semiconductor to 9.7 kilometers per second in 2004. Hau later succeeded in stopping light completely, and developed methods by which it can be stopped and later restarted. This was in an effort to develop computers that will use only a fraction of the energy of today's machines.
In 2005, IBM created a microchip that can slow down light, fashioned out of fairly standard materials, potentially paving the way toward commercial adoption.
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