Fig. 1. Basic principle of DAVLL. (a) Two-level atomic model; (b) σ⁺ and σ^- transmission spectra; (c) dispersion-like spectral lines

Fig. 2. Schematic diagram of small cesium atomic fountain clock

Fig. 3. Physical pictures of laser frequency stabilization and amplification modules. (a) Front view; (b) top view

Fig. 4. Laser frequency stabilization module

Fig. 5. Laser amplification module

Fig. 6. Laser beam splitting module

Fig. 7. Spectral line signal

Fig. 8. Flow chart of automatic frequency stabilization and shift in laser system

Fig. 9. Error signals of frequency stabilization and shift

Fig. 10. Cold atom number signal over 24 h