Physics 2000 The Atomic Lab Bose Einstein Condensation

Laser Cooling

Doesn't shining light on something make it hotter, not colder?

Shining light on your hand makes it get hotter because the light is absorbed and turns into heat. The trick to making atoms colder is to make the light bounce off of them.In fact, it bounces off with more energy than when it hits the atoms.

That sounds like quite a trick.

It is. It took physicists quite a while to figure out how to do it. (Click here to find out more about laser cooling and the winner of the 1997 Nobel Prize for Physics.) You start with the idea that laser light comes in a stream of photons. These photons are very light, so to speak. Compared to an atom, they are like ping-pong balls compared to a bowling ball. But in just the same way you can push a bowling ball around if you shoot a big enough stream of ping-pong balls at it, you can push atoms around by bouncing laser light off them. Try to adjust the laser power and laser position to slow down the atoms.




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