Fig. 1. Control structure diagram of an iodine-stabilized laser

Fig. 2. DDS schematic diagram

Fig. 3. Spectrum diagram with higher-order harmonics

Fig. 4. Spectrum diagram of the modulated signal generated by DDS

Fig. 5. Block diagram of the signal demodulation algorithm

Fig. 6. (a) Demodulation curve of the iodine cell with non-saturated absorption; (b) Demodulation curve of the iodine cell with saturated absorption

Fig. 7. Schematic diagram of second harmonic detection of the absorption peak

Fig. 8. Absorption peak identification algorithm flowchart

Fig. 9. Second harmonic absorption peak curve

Fig. 10. f-peak identification and locking curve

Fig. 11. (a) Output of the PID control signal with poor parameter tuning; (b) Corresponding beat frequency

Fig. 12. (a) Output of the PID control signal with good parameter tuning; (b) Corresponding beat frequency

Fig. 13. Schematic diagram of absolute frequency measurement based on an optical frequency comb

Fig. 14. (a) Beat frequency of a non-saturated laser based on an optical frequency comb; (b) Allan variance of the non-saturated laser

Fig. 15. (a) Beat frequency of a saturated laser based on an optical frequency comb; (b) Allan variance of the saturated laser

Fig. 16. Frequency reproducibility of the iodine-stabilized laser