An atomic clock based on coherent population beating

We demonstrated an atomic clock based on coherent population beating (CPB). CPB occurs in typical Λ system, which enables us to obtain the beat frequency of the radio frequency for laser modulation and the hyperfine splitting. The beat frequency and its fluctuation is detected and accurately measured through digitized processing for compensating the shift of the radio frequency. It enables us to achieve a standard frequency which directly reference to the hyperfine transition. In our preliminary experiment an Allan Deviation of 3e-12 at 1000s is observed. CPB atomic clock eliminates the phase locking loop, and can be easily digitized and integrated.