Fig. 1. Physical image of laser and linewidth test diagram

Fig. 2. Schematic diagram of the laser optical path

Fig. 3. Drive circuit and control algorithm

Fig. 4. Frequency tuning range by adjusting the heating resistor of the FP microcavity

Fig. 5. Waveform states of the heating resistor of the FP microcavity at different voltages. (a) 2 V; (3) 3 V

Fig. 6. Linear relationship between two phases

Fig. 7. Frequency tuning range after phase compensation

Fig. 8. Frequency tuning range after current compensation