The pulsed optically pumped Rb frequency standards in National Time Service Center

In this paper we report a laboratory prototype of pulsed optically pumped (POP) rubidium frequency standard. In POP operation the pumping, interrogation, and detection phases are separated in time, avoiding the coupling between microwave and optical coherence. The POP 87Rb vapor-cell frequency standard was studied experimentally based on the detection of free induction microwave signal or optical absorption signal. Ramsey fringes were obtained based on 87Rb in buffer gas, with FWHM of 65Hz and 150Hz for microwave and optical central Ramsey fringes respectively. The atomic quality factor was on the order of 108. With microwave detection, the achieved frequency stability was 1.2×10-12τ-1/2(τ=1~100s).