With a coupling laser locked to caesium 6S1/2 Fg=4-6P3/2 Fe=5 cycling transition and a co-propagating probe laser scanned across 6S1/2 Fg=4-6Pa/2 Fe=3, 4 and 5 transitions, a novel scheme for sub-Doppler spectra in Dopplerbroadened V-type three-level system is demonstrated by detecting the transmission of the coupling laser through a caesium vapour cell. The Autler-Townes doublet in the sub-Doppler spectra of the coupling laser is clearly observed. The effects of coupling laser intensity on the splitting and linewidth of the Autler-Townes doublet are experimentally investigated and the results agree well with theoretical predictions. Taking the multiple hyperfine levels of caesium atom into account, a brief analysis is presented.
Single caesium atoms in a large-magnetic-gradient vapour-cell magneto-optical trap have been identified. The trapping of individual atoms is marked by the steps in fluorescence signal corresponding to the capture or loss of single atoms. The typical magnetic gradient is about 29 mT/cm, which evidently reduces the capture rate of magneto-optical trap.
Based on our work on single cesium atoms trapped in a large-magnetic-gradient vapour-cell magneto-optical trap （MOT）, the signal-to-noise ratio （SNR） is remarkably improved. Also a far-off-resonance optical dipole trap （FORT） formed by a strongly-focused 1064 nm single frequency Nd：YVO4 laser beam is introduced. One cesium atom is prepared in the MOT, and then it can transfer successfully between the MOT and the FORT which is overlapped with the MOT. Utilizing the effective transfer, the lifetime of single atoms trapped in the FORT is measured to be 6.9± 0.3 s. Thus we provide a system where the atomic qubit can be coherently manipulated.
