Cooling on a two-photon transition with an optical frequency comb is published. In Wes Campbell’s Lab at UCLA we demonstrated that by driving a two-photon transition the entire power of an optical frequency comb can be utilized to laser cool and trap atoms. We developed the technique (using rubidium) for cooling atoms with deeply bound valence electrons such as hydrogen and carbon for precision measurement and quantum chemistry. Please see our paper
John Barry, the master of laser cooling molecules, wrote a Physics Viewpoint article covering our research.