Qiang Hao , Wenxiang Xue, Wenbing Li, Feng Xu, Xin Wang, Wenge Guo, Peter Yun, and Shougang Zhang

Abstract: We report a high-performancepulsed optically pumped (POP) Rb clock based on a novel magnetrontype microwave cavity. The cavity has a volume of 30 mL, enabling a highly homogenous microwave field distribution. With the laser frequency tuning to the ground-state hyperfine level F = 2 of the D₂ line, we observe a Ramsey fringe contrast of 52% in terms of optical absorption detection. The resultant shot noise limit is estimated to be 1.6×10^-14τ ^-1/2. The clock frequency
stability is measured as 2.3×10^-13τ ^-1/2 (1-100s), which is limited by the relative intensity noise of the light.

Key words: Atomic clock, frequency stability, magnetron-type cavity, optical pumping, signal contrast.