Fig. 1. Structural diagram of external-cavity diode laser

Fig. 2. External mirror. (a) Structural diagram; (b) optical micrograph

Fig. 3. Operation principle of mirror. (a) k² value of DC and mirror reflectivity versus wavelength with equivalent mirror structure shown in inset; (b) mirror reflectivity versus phase shift in MZI arm under different k²

Fig. 4. Simulation results of vernier filter. (a) Side-mode suppression ratio versus wavelength tuning range; (b) normalized transmission spectra of MRR₁, MRR₂, and d-MZI; (c) normalized transmission spectrum of external-cavity mirror without d-MZI; (d) normalized transmission spectrum of external-cavity mirror

Fig. 5. Schematic of external-cavity diode laser measurement system

Fig. 6. Gain spectrum of RSOA with driving current of 120 mA

Fig. 7. Basic characteristics of laser. (a) L-I curve of external-cavity diode laser; (b) laser output spectrum

Fig. 8. Performance test results of laser. (a) Laser output power versus V_TC; (b) laser operating wavelength versus V_PS; (c) superimposed

Fig. 9. Laser output spectra under different V_TC when V_MRR1=6 V. (a) V_TC=0 V; (b) V_TC=30 V