Low power chip-scale CPT atomic clock with new microwave frequency modulation technique

We present a new chip-scale atomic clock with low power consumption based on a new microwave frequency modulation technique achieved with the voltage-control oscillator (VCO) and the new servo circuit designed for frequency-locking the microwave to an ⁸⁵Rb coherent population trap (CPT) atomic resonator. The microwave modulation is achieved by directly injecting triangular current signal into the charge-pump of the phase-locked loop. The system volume is less than 50 cm³ and the total power consumption of the whole system is less than 600mW. Experiments on frequency stability are performed under laboratory environment, and the results show that the frequency stability (overlapping Allan deviation) of the 10 MHz output signal reaches 2×10^-10 at average time of 1 s, and 5×10^-11 at average time of 1000 s. These results reveal that our atomic clock is practical for most applications that require compact, high stable and low-power consumption frequency sources.