Active Suppression of the Light Shift in an Atomic Clock Based on Coherent Population Trapping in 87Rb Vapor Using the Phase Jump Technique

Abstract

The active suppression of light shift of the reference coherent population trapping (CPT) resonance in 87Rb vapor to improve the long-term stability of compact atomic clocks has been demonstrated experimentally. The approach is based on the phase jump technique used to synthesize an error signal, which is proportional to the light shift of the CPT resonance, from an optical transmission signal. The use of this error signal in an additional feedback loop allows one to stabilize the amplitude of a microwave signal for the phase modulation of laser radiation near a value at which the light shift of the CPT resonance is absent. This technique has made it possible to reduce the long-term instability of CPT atomic clocks in our experiments by a factor of 15 at an integration time of 10 000–20 000 s.