Laser Cooling
When somebody mentions the word “laser”, what image is conjured in your mind? A laser gun? Battleships roaming around the eerie ground?
It turns out that laser cooling is extremely effective to reduce the temperature of atoms or molecules near absolute zero. However, these atoms can not be cooled to reach absolute zero, which is explained in my previous article.
Methods
“All roads lead to Rome”. There are various methods to laser cool an atom, with the most prominent one being Doppler Cooling. The following non-extensive list shows a few laser cooling method:
- Doppler cooling
- Sisyphus cooling
- Cavity mediated cooling
- Use of a Zeeman slower
- Electromagnetically induced transparency (EIT) cooling
- Anti-Stokes cooling in solids
- Polarization gradient cooling
Applications
Laser cooling is applied to help scientists perform experiments in temperatures in the vicinity of absolute zero. At this temperature, unique quantum effects such as Bose–Einstein condensation or superfluidity can be observed.
Here is a video demonstrating superfluidity:
Sucess Stories
In the past, laser cooling is limited to atoms, but scientists have progress towards laser cooling more complex systems.
- 2007: MIT laser-cooled a macro-scale object weighing 1 gram to 0.8 K.
- 2010: Yale laser-cooled a diatomic molecule.
- 2011, a team from both the California Institute of Technology and the University of Vienna laser-cool-ed a mechanical object with a size of 10 μm x 1 μm to its quantum ground state.
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