Turnkey Soliton Microcombs via Self‐Injection Locking in Dual‐Coupled and Interferometric Microring Systems

This study systematically investigates, via numerical simulations, the self‐injection locking (SIL) characteristics of dual‐ring coupled cavity systems and interferometric microring systems. For the dual‐ring system, we show that the SIL region on the tuning curve splits into two distinct subregions, governed by the inter‐ring coupling coefficient and the central‐frequency detuning. Using the Turnkey method, we demonstrate spontaneous generation of single‐soliton combs, and achieve a conversion efficiency of 60% in a Vernier dual‐ring configuration with an FSR ratio of 5.1. For the interferometric microring (U‐shaped feedback arm), we show that SIL enables high‐probability reproducible generation of soliton crystals with pulse numbers tunable from 4 to 8 via the transmission phase, with conversion efficiencies ranging from 67% to 88%. The upper limit of the soliton number can be further extended by dispersion engineering. In addition, repeated Turnkey simulations reveal that SIL significantly biases the probability distribution of final soliton‐crystal states, and perturbation‐recovery tests demonstrate the robustness of the selected states against parameter fluctuations. We also observe that the SIL effect is nearly suppressed at specific circular phase configurations.