In order to exploit its potential applications, we experimentally study the dependence of 85 Rb-based coherent population trapping (CPT) resonance on N 2 buffer gas with 6 vapor cells filled with natural rubidium and N 2 . The experiments are carried out at different pressures and temperatures, and the results reveal that higher cell temperature makes the resonance more sensitive to N 2 pressure. Thus, it is important to choose a proper buffer gas pressure at a given cell temperature. This work provides valuable data for the application of 85 Rb CPT resonance with a buffer gas of N 2 .
We report our experiment on sideband cooling with two Raman transitions in a $\mathrm{\ensuremath{\Lambda}}$ configuration that allows selective coherent population trapping (CPT) of the low-lying motional states. The cooling method is applied to
87Rb atoms in a circularly polarized one-dimensional optical lattice. Owing to the vector polarizability, the vibration frequency of a trapped atom depends on its Zeeman quantum number and the CPT resonance for a pair of bound states in the $\mathrm{\ensuremath{\Lambda}}$ configuration depends on their vibrational quantum numbers. We call this scheme motion-selective coherent population trapping (MSCPT) and it is a trapped-atom analog of the velocity-selective CPT developed for free He atoms. We observe a pronounced dip in temperature near a detuning for the Raman beams to satisfy the CPT resonance condition for the motional ground state. Although the lowest temperature we obtain is ten times the recoil limit owing to the heat load from motion along an axis, which is left uncooled, and the large Lamb-Dicke parameter of 2.3 in our apparatus, the experiment demonstrates that MSCPT enhances the effectiveness of Raman sideband cooling and enlarges the range of its application. Discussions of design parameters optimized for MSCPT on
87Rb atoms and opportunities provided by diatomic polar molecules, whose Stark shift shows a strong dependence on the rotational quantum number, are included.
Abstract A theory is developed for the effect of coherent population trapping (CPT) in ‘hot’ atoms under pulsed pumping in an optically dense medium with a buffer gas. The case is considered when the excited level is not degenerate. Based on an analysis of the shape of Ramsey resonances, we show that with increasing optical density of the medium, the dependence of the light shifts of the CPT resonance becomes more and more nontrivial. The dependence of the light shifts of the CPT resonance on the magnitude of the hyperfine splitting of the excited level, concentration of active atoms, temperature, and duration of the dark pause is constructed.