<sup>85</sup>Rb D1-line CPT atomic clock with low power consumption

Abstract

This paper describes the investigation of a 85Rb D1-line coherent population trapping (CPT) atomic clock with a Rb gas-cell containing a natural mixture of Rb atoms and buffer gas. The choice of 85Rb rather than conventional 87Rb is dictated by the lower ground-state hyperfine-splitting frequency, which leads to less than one-half the required RF power and more effective RF-related circuit designs. In this paper, the modulation profiles, the CPT resonances, and the long-term frequency stabilities of the CPT resonance for 85Rb D1 and D2 lines are presented. The frequency deviations for D1 and D2 lines are measured using a same experimental setup except for VCSEL wavelength and RF power. The Allan deviations, estimated from the frequency deviations, are ≪ 2.5×10−12/day for D1 line and ≪ 4.0×10−12/day for D2 line. In the case of D1 excitation, required RF frequency is 1.5 GHz and its power is only −8.0 dBm.