Improving the short-term frequency stability of a magnetic-state-selected cesium beam clock with optical detection

The microwave spectrum line shape and the signal-to-noise ratio of a compact optically detected magnetic-state-selection cesium beam clock are analyzed in this paper. As the noise analysis shows, the performance is related to the atomic utilization ratio and locking parameters when the laser frequency noise is the dominant noise source. Methods are adopted for realizing better short-term frequency stability of the clock, including using a highly efficient state-selection cesium beam tube, optimizing the locking parameters, and stabilizing the microwave power to maximize the error signal. After optimization, the signal-to-noise ratio of the clock reaches 7.0 × 10³ in a bandwidth of 1 Hz and the clock demonstrates a short-term stability of 4.1 × 10^-12 τ^-1/2. The five-day Allan standard deviation reaches 7.7 × 10^-15.