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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 85 Rb 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 cm 3 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.

The optoelectronic oscillator (OEO) uses an optical energy storage element to achieve high quality microwave signals which are spectrally pure. But in some applications, the stability loss and large physical size become considerable problems. To solve these problems, we present an approach of building chip-scale atomic resonator-based stabilization system for optoelectronic oscillators. This system is mainly made up of chip-scale CPT atomic clock and enhanced PLL synchronization circuits. We lock the oscillation of OEO to a high stable microwave reference which is synchronized from CPT atomic clock. In our system, we obtain a stable 3.035 GHz microwave signal with a short-term frequency instability of 2×10 -10 (1 s) and a long-term instability of 5×10 -11 (1000 s). The whole physics package of the stabilization system is 4.5 cm×4.5 cm×2 cm.

We demonstrated the observation of Rb two-photon absorption directly excided by an optical frequency comb at fiber communication bands. A chain of comb spectral control is elaborately implemented to increase the power of the second harmonic optical frequency comb generation and the two-photon transition strength. A two-photon transition spectrum is obtained with clearly resolved transition lines. It provides a potential approach to realize the optical frequency comb or optical clock at ~1.5{\mu}m with high stability and accuracy., Comment: 7 pages, 3 figures