Optical frequency comb generation through a thermal assisted method in a Si3N4 microresonator

Optical frequency combs in dissipative Kerr soliton state can exist stably in a high Q-factor nonlinear cavity when a continuous wave pump laser is coupled to the microresonator as long as the double balance between anomalous cavity dispersion and kerr nonlinearity, and cavity loss and parametric gain is realized. However, due to the thermal instability of the microresonator, the generation and survival of the DKS requires keeping the pump at effective red-detuned regime. In this paper, in order to overcome the thermal instability when the intracavity power changes as the pump wavelength swept from blue-detuned to red-detuned with respect to a resonance of the microresonator, we adopt the thermal-assisted method, using an additional stable narrow linewidth laser as an assisted laser. We have studied the different mechanism of Optical frequency combs generation based on an opposite-directional pump configuration, According to the experimental results, two different initial comb states observed in the Si3N4 microresonator, but only one initial state can lead to stable Optical frequency comb generation. By adjusting the input power and stopping wavelength of the assisted laser and the pump laser respectively and properly, we observe the “step-like” transmission in our Si3N4 microresonator.