Text: Researchers break record for stopping light in its tracks a.. 11 June 2005 LIGHT travelling through a solid has been stopped in its tracks for more than a second. This is a thousand times longer than the previous record set in gases. To stop light in a gas, physicists use a "coupling" laser to nudge the atoms of the gas into a special quantum state that prevents the atoms from interacting with the light. Lower the intensity of the coupling laser, and light pulses travelling through the medium can be slowed down and even halted. Raise the laser's intensity and the light starts moving again. However, the difficulty in maintaining the quantum state had meant that light could be stopped for less than a millisecond. Last year a team from the Australian National University in Canberra sustained such quantum states for tens of seconds in yttrium silicate that was doped with praseodymium. And on 26 May, team member Jevon Longdell announced at the Conference on Lasers and Electro-Optics in Baltimore, Maryland that they had stopped light in the same material for more than a second. The solid had to be cooled to a few degrees above absolute zero, which means the set-up can't be used for anything practical, says Longdell. "The temperatures would need to get up to liquid nitrogen temperatures [about 80 °K] for any real benefit." http://www.newscientist.com/channel/fundamentals/mg18625035.400

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