Dispersive-wave-assisted sideband self-injection locking of soliton microcombs

Soliton microcombs have emerged as a promising integrated light source for applications ranging from coherent communications to precision metrology. However, their coherence remains limited by intrinsic and technical noise. While conventional two-point locking techniques can suppress these noises by simultaneously stabilizing both the pump and a sideband comb line, they typically require two external lasers, complicating system integration. In contrast, sideband self-injection locking (SSIL) achieves stabilization with only a single pump laser by feeding a selected comb line back into the cavity. This approach not only narrows the linewidth of the target comb line but also reduces the soliton timing jitter through optical frequency division. However, existing SSIL implementations demand high feedback ratios and suffer from significant insertion loss in the feedback loop, necessitating optical amplifiers and undermining system simplicity. Here, we present a systematic numerical study demonstrating that locking the feedback loop to a dispersive wave (DW) generated via soliton Cherenkov radiation drastically reduces the required feedback ratio by over an order of magnitude. This reduction arises from the DW's enhanced coupling and intracavity power, enabling efficient SSIL with low optical feedback. Consequently, the stringent optical amplifier requirement is eliminated, allowing fully passive stabilization. Our work deepens the understanding of SSIL dynamics in Kerr combs and provides a feasible, power-efficient strategy for stabilizing soliton microcombs in chip-scale systems.