Question: Is it possible to make a laser that is cold? Tell me Why.

Euan Allen answered on 13 Jun 2016:

Hi Nintega21!

Great question – it depends on what part of the laser you want to make cold.

My lasers in my lab actually need to be kept cool because they can heat up pretty quick and can then stop working completely. We do this by pumping lots of cold water through the hot parts of the laser. You usually don’t want to make these parts too cold though, as that will also stop them from working.

One really interesting thing you can do with lasers though, is you can actually cool other things down with them, like for example a gas. We do this through a process known as ‘laser cooling’. What we do is cleverly trap the gas in a cup like shape, and we allow the hot atoms to escape out the top, leaving just the cool atoms behind. This has the effect of creating a very cold region of gas left over in the trap (it’s the same as when you leave a cup of tea out for too long and the steam escapes out the top). This technique can usually make the gas around -273 degree Celsius, which is the cooler than any natural thing in the universe!