Stability properties of an Rb CPT atomic clock with buffer-gas-free cells under dynamic excitation

Abstract

This work presents a study of the short-term stability properties of Rb atomic clocks based on coherent population trapping (CPT) under dynamic excitation of a CPT resonance in cells without buffer gas. It is demonstrated that in an optical cell with anti-relaxation coating of its inner walls, the best stability is achieved at the scanning frequency of the frequency difference of the bichromatic pump field equal to 2 kHz at the resonance width of 450 Hz. In cells without a wall coating, the optimal scanning frequency range is found to be 1.2–2.8 kHz at the resonance width of 29 kHz. Examination of the slope of the stabilization system’s discriminant curve at zero error signal for buffer-gas-free cells uncovered an amount of correlation between the discriminant curve slope and atomic clock stability. It is demonstrated that the highest stability of atomic clocks in dynamic excitation mode is achieved at a ratio of scanning frequency and amplitude around 1.