Fig. 1. Schematic diagram of the PDH laser frequency stabilization technique

Fig. 2. Block diagram of the PDH digital frequency stabilization system

Fig. 3. Flow chart of frequency stabilization process

Fig. 4. DDS wave generator with jitter injection

Fig. 5. Block diagram of the digital coherent demodulation

Fig. 6. Block diagram of the digital orthogonal demodulation

Fig. 7. PDH discriminant signal using MATLAB simulation

Fig. 8. Frequency discriminant signal acquired through experiments

Fig. 9. Flow chart of backward difference peak-finding algorithm

Fig. 10. Block diagram of a single-loop digital feedback control system

Fig. 11. Flow chart of the incremental digital PID algorithm

Fig. 12. Digital frequency stabilization experimental system and FPGA hardware PCB

Fig. 13. Signals during the frequency scan process

Fig. 14. Process of automatic transition from scan to lock

Fig. 15. Enlarged view of the second scan cycle

Fig. 16. Laser frequency drift in digital frequency stabilization

Fig. 17. Floor noise measurement results of the FPGA circuit board