Ramsey-CPT spectroscopy for a microcell atomic clock
Résumé
We investigate the use of pulsed Ramsey-CPT spectroscopy in a coherent population trapping (CPT) atomic clock using a microfabricated buffer gas-filled Cs vapor cell. Tests are performed on a table-top setup with an external acousto-optical modulator (AOM) to produce the optical CPT pulse sequence. A relevant reduction of the clock frequency sensitivity to laser power variations by a factor of about 40 is observed, in comparison with the standard continuous-wave (CW) regime, with a free-evolution time T = 450 μs. The dependence to microwave power variations is also reduced in the Ramsey-CPT interrogation case. With the same cell physics package and similar environmental conditions, the clock Allan deviation is clearly improved for time scales higher than 100 s in the Ramsey-CPT case. These results suggest that the use of Ramsey spectroscopy might be an attractive approach in miniature clocks
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