Fig. 1. Schematic diagram of (a) two-ring Vernier and (b) two-ring Vernier with MZI tunable laser. Electrical contacts are shown in gold.

Fig. 2. (a) LIV characteristics of the Vernier ring laser when both rings are unbiased. (b) Spectral characteristics showing ring mode hops and cavity mode hops. (c) OSA trace at 290 mA drive current (curve has been truncated in the middle) showing both ground state and excited state lasing can be observed. (d) LIV characteristics of the Vernier ring laser when ring one is unbiased and ring two has 45.8 mW electrical power applied. (e) Spectral characteristics showing only cavity mode hops. (f) OSA trace at 290 mA drive current showing only ground-state lasing.

Fig. 3. (a) LIV characteristics of the Vernier ring MZI laser. (b) Spectral characteristics showing cavity mode hops.

Fig. 4. Lasing wavelength as a function of the applied heater power for (a) the first ring and (b) the second ring.

Fig. 5. Tuning map of the Vernier ring laser showing (a) peak wavelength and (b) SMSR.

Fig. 6. Vernier ring laser: (a) automatically measured spectra over the entire tuning range and (b) manually optimized spectrum at a single point showing 52 dB SMSR.

Fig. 7. Vernier ring MZI laser: (a) automatically measured spectra over the entire tuning range and (b) manually optimized spectrum at a single point showing 58 dB SMSR.

Fig. 8. (a) Coefficients A, B, F calculated for the Vernier ring laser cavity as functions of detuning from the ring resonance peak with αH=2. (b) Estimated Lorentzian linewidth as a function of linewidth enhancement factor. A waveguide loss of 5 dB/cm and an output power of 10 mW were used in the calculation.

Fig. 9. Measured Lorentzian linewidth as a function of wavelength for (a) Vernier ring laser and (b) Vernier ring MZI laser.

Fig. 10. Measured frequency noise of the Vernier ring MZI laser in logarithmic scale over complete frequency range.