Self-cooling, blue-detuned dissipative Kerr microresonator soliton comb

Dissipative Kerr solitons (DKSs) generated in high-Q microresonators driven by continuous-wave (CW) lasers provide chip-scale optical frequency combs composed of mutually coherent CW lines. However, their small mode volume makes them highly susceptible to thermal fluctuations, and the resulting thermo-refractive noise perturbs the repetition rate, frep. Here, we experimentally demonstrate a “blue-detuned” DKS in a coupled-ring microresonator. By employing avoided-mode-crossing-induced dispersion engineering at the pump mode, DKSs are generated even when the pump laser is tuned to the higher-frequency (blue) side of the resonance. In this regime, the pump laser not only seeds DKS formation but also serves as a cooling laser for the thermally sensitive pumped mode. We observe a self-cooling effect that reduces the phase noise of frep by up to 14.5 dB, while achieving a pump-to-comb conversion efficiency as high as 37%. These results establish blue-detuned DKSs as a thermally robust and power-efficient solution for integrated microcomb systems, eliminating the need for auxiliary lasers.