Mitigation of thermal instabilities in Kerr microcombs

Dissipative Kerr solitons in microring resonators have the potential to enable precision measurements with optical frequency combs in an integrated photonics package. However, the small volume of these resonators makes them highly susceptible to thermorefractive effects. We present a system of two coupled resonators that reduces the effect of thermal shifts on comb states through controllable mode crossings and fast detuning control of the pump laser. Both methods aim to beat the thermal timescale of the resonator to stabilize a dispersive Kerr soliton. Using soliton lifetime as a metric, we find increased resilience to thermorefractive effects when the pump laser is swept faster than the thermalization timescale of the cavity and when mode frequencies in the auxiliary resonator at or near the pumped mode are tuned towards degeneracy with the main resonator (i.e. the resonator with the soliton). The lifetime near an auxiliary resonator-main resonator mode crossing shows a three order of magnitude increase from the native soliton lifetime set by the thermalization time of a single resonator. These results suggest that both methods can be used to reduce thermorefractive phase noise in soliton microcombs.