Accessing Soliton Microcombs With Pump Phase Modulation Switch

ABSTRACT Microresonator‐based optical frequency combs have evolved to be key laser sources in advanced applications, including telecommunications, optical computing, and LiDAR. Yet, they face challenges in accessing the fully coherent dissipative soliton state due to the competing effect between Kerr and thermal nonlinearities. Although a number of efforts have been reported to manage the thermal equilibrium of the system in order to promote the accessibility of the soliton state, this leaves an increased complexity, particularly in having additional components that are non‐trivial to be removed or switched off. Here, we demonstrate a removable thermal compensation approach to accessing the soliton state. The approach is based on the pump phase modulation in which the modulation sideband would act to maintain the thermal equilibrium and extend the soliton existence range. More importantly, switching off the modulation would lead to the power recovery of the CW pumping as the carrier, which would counterbalance the system cooling and secure the soliton existence. By unveiling the physics and demonstrating the approach at both optical C‐ and O‐bands, our work represents a crucial advance in maintaining the clarity of soliton microcombs with eliminated noise from auxiliary lasers or radio frequency modulations, which would benefit coherent comb applications.