Frequency Stability of Atomic Clocks Based on CoherentPopulation Trapping Resonance in 85Rb

Abstract

An atomic clock system based on coherent population trapping (CPT)resonance in 85Rb is reported, while most past works about theCPT clock are in 87Rb. A new modulation method(full-hyperfine-frequency-splitting modulation) is presented to reducethe effect of light shift to improve the frequency stability of the CPTclock in 85Rb. The experimental results show that the short-termfrequency stability of the CPT clock in 85Rb is in the order of10−10/s and the long-term frequency stability can achieve1.5×10−11/80000 s, which performs as well as 87Rb in CPTresonance. This very good frequency stability performance associatedwith the low-cost and low-power properties of 85Rb indicatesthat an atomic clock based on CPT in 85Rb should be a promisingcandidate for making the chip scale atomic clock.