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Q & A: slowing light

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Most recent answer: 10/22/2007
Q:
I read that Bose-Einstein condensates have actually been found to slow the passage of light. Why is it slowed instead of being absorbed like under normal circumstances? (with normal matter) P.S. Are scientists looking to create these condensates at warmer temperatures? What would that require?
- Gill (age 43)
Dayton
A:
Actually, light slows down as it travels through glass or water, etc. Not much is absorbed there either. Some of the new cold materials are special only in that light slows down a great deal in them. The basic reasons are similar to the reasons light slows down in anu ordinary material. The relation between the slowing and the light absorption (Kramers-Kronig) does not directly require that there be absorption at all frequencies, although the maximum effect on the speed occurs for frequencies close to ones that are strongly absorbed.

I'm not aware of attempts to push the Bose condensation temperature very much higher. The Bose condensation temperature is set by the mass of the particles (not really adjustable) and their density, which is limited by interparticle interactions. So this can't be easily changed.

Mike W.

(published on 10/22/2007)

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