Mid-infrared optical solitons may be a powerful tool for applications in on-chip integrated photonics and spectroscopy, as they provide broadband, phase-locked frequency combs. Quantum cascade lasers (QCLs) embedded in a ring cavity have been found to enable self-starting optical soliton generation. In order to study these phenomena numerically, we use a model based on coupled Maxwell-density matrix equations. The introduction of backscattering in our model stabilizes self-assembled soliton field solutions, which is in very good agreement with experimental data. In this contribution, we present our model and discuss the mechanisms that lead to soliton operation in ring QCLs.
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