Fig. 1. Conceptual representation of the optical loss in the microresonator at low power

Fig. 2. (a) Schematic diagram of the silicon nitride microring resonator before redeposition of film, silica protective layer has been deposited above the coupling waveguide; (b) Side view of the silicon nitride microring resonator with the redeposited film

Fig. 3. (a) Statistical histograms of intrinsic Q of silicon nitriding microring resonator before (blue histogram) and after (orange histogram) deposition of thin films, which includes intrinsic Q of all fundamental TM modes between 1550 nm and 1625 nm; (b)-(c) The transmission power spectrum of the optical mode with the highest intrinsic Q before and after the redeposition. The loaded Q by Lorentz fitting is 2.84×10⁶ and 3.44×10⁶, respectively, and the corresponding intrinsic Q is 2.91×10⁶ and 4.15×10⁶, respectively

Fig. 4. (a) Transmission spectrum of the TM mode in the silicon nitride microring resonator; (b) The change of the intracavity power and the transmitted power with the pump light sweeping from the blue detuning to the red detuning, where distinct soliton steps can be observed; (c) The generated spectral spectrum of the soliton microcomb, the envelope perturbation is caused by avoided mode crossings; (d) The spectral spectrum of the soliton microcomb and the corresponding integrated dispersion curve, the dispersion abrupt change on the dispersion curve corresponds to the envelope perturbation on the soliton microcomb spectrum