mu POP Clock: A Microcell Atomic Clock Based on a Double-Resonance Ramsey Scheme

We demonstrate and study a microcell microwave atomic clock based on optical-microwave double resonance (DR) interrogation operated in a pulsed Ramsey scheme, called the mu POP clock, based on a microfabricated Rb vapor cell and a micro-loop-gap microwave resonator. For the mm-scale dimensions of this cell, the population and coherence relaxation rates of the Rb clock transition are on the order of 4-5 kHz, which puts constraints on the useful Ramsey times and overall pulse sequence in view of optimized clock performance. Our proof-of-principle demonstration of the mu POP clock shows that the pulsed DR approach is nevertheless feasible and results in a short-term clock stability of 1 x 10(-11) tau(-1/2) and reaching the