Fig. 1. The calculated MTS signal at different modulation frequencies ω_m

Fig. 2. The extreme point-to-point amplitude curve near the zero point of the MTS signal at different modulation frequencies

Fig. 3. Schematic diagram of laser frequency lock based on MTS spectrum

Fig. 4. Comparison between the MTS spectral and the saturated absorption spectral

Fig. 5. Modulation and demodulation circuit principle of MTS signal

Fig. 6. The simulated and measured MTS signal vary with the different demodulation phases φ

Fig. 7. The relationship between the amplitude of the MTS signal and the angle between the polarization of the pump light and the probe light

Fig. 8. Relationship between solenoid current and MTS signal amplitude

Fig. 9. Linewidth of DFB laser before and after MTS frequency locking