Laser cooling with three-level cascade transitions: a study for group II atoms and ytterbium

We analyze laser cooling of two-electron atoms with three-level cascade transitions, involving the usual ¹S₀–¹P₁ cooling transition coupled to either ¹S₀ or ¹D₂ states. We numerically calculate minimum temperatures for the most abundant even isotopes of group II atoms and ytterbium (which lack hyperfine structure), derive general analytical expressions from a perturbative approach, and discuss the experimental implementation of the technique. Considered as an alternative 2nd stage technique to intercombination line cooling, three-level cooling is clearly advantageous for light elements, such as Mg and Ca, while for all elements provides much higher capture ranges, increasing the transfer efficiency from the 1st stage cooling, with faster cooling times and sub-Doppler temperatures. (paper)