Description
Optical frequency combs generated in driven passive microresonators are central to applications in spectroscopy, metrology, and communications, and are promising for on-chip integration [1]. These microcombs often take the form of soliton crystals (SCs), ordered ensembles of ultrashort pulses known as cavity solitons [1,2]. In microresonators, SC formation is usually enabled by avoided mode crossings (AMXs), spectrally localized perturbations of the resonator dispersion [2]. Despite the central role of AMXs in SC formation, their precise influence and the underlying physical mechanisms remain poorly understood. Existing studies are largely experimental, with theoretical investigations mainly focused on reproducing specific experiments through numerical simulations [2,3].
Here, we develop such an understanding through a comprehensive theoretical framework based on the Lugiato-Lefever equation, modified to include the effect of an AMX [4]. Combining dynamical simulations with a stability analysis of the stationary solutions, we identify the different physical mechanisms through which AMXs promote SC formation. We show that an AMX can: (i) stabilize soliton-crystal states that are unstable in its absence; (ii) modify the periodicity of the pattern solutions through a pinning mechanism, enabling them to act as seeds for soliton-crystal states that would not form without the AMX; (iii) reshape the modulation-instability gain spectrum, leading to the emergence patterns that are not supported in the absence of the AMX. Finally, we provide a practical recipe for selectively generating perfect or imperfect soliton crystals by controlling the AMX’s spectral position and strength. Because these states are desirable for different applications, this capability maximizes their practical impact.
[1] A. Pasquazi et al., Physics Reports 729, 1–81 (2018).
[2] D. C. Cole et al., Nat. Photonics 11, 671–676 (2017).
[3] M. Karpov et al., Nat. Phys. 15, 1071–1077 (2019).
[4] C. Silvestri et al., arXiv:2606.03202 (2026).
| I am the presenting author | Yes |
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