Sub-Doppler cooling made more simple

Our former MPhys student, Matthew Johnson, supervised by Graham Bruce and Brendon Lovett, had his thesis work included in a recent publication in J Phys B [1].

In collaboration with the Kuhr group at University of Strathclyde and Saijun Wu at Fudan University, they have uncovered a simple way to realise low temperatures of laser cooled potassium.

The isotopes of potassium have traditionally been hard to laser cool in large numbers to particularly low temperatures, due to their poorly resolved hyperfine structure. In recent years, however, a number of groups discovered that by using a particular combination of laser frequencies to pump atoms into velocity-selective dark states, low temperatures could be realised.  All these techniques required additional lasers to create these dark states, but Matt and team realised that the same physics can be realised using the same lasers as are already in use for initial cooling.  The technique looks to also be applicable to the other alkali atom with particularly poor hyperfine resolution: lithium.

[1] Sub-Doppler laser cooling of ⁴⁰K with Raman grey molasses on the D₂-Line
G. D. Bruce, E. Haller, B. Peaudecerf, D. A. Cotta, M. Andia, S. Wu, M. Y. H. Johnson, B. W. Lovett & S. Kuhr
J. Phys. B: At. Mol. Opt. Phys. 50, 095002 (2017)