Counter-Propagating Solitons in the Mode-Splitting Microcavity

Optical Kerr solitons in high-quality microcavities offer broadband spectrum, high repetition rates, compact integration and low power thresholds, making them critical tools for precision metrology. However, generating stable Kerr solitons requires ultrahigh-Q microresonators to minimize fabrication-induced losses and mitigate parasitic Rayleigh backscattering. We investigate counter-propagating soliton formation in mode-splitting cavities, where Rayleigh backscattering enables self-thermal equilibrium stabilization within specific red-detuned regimes and strong local perturbed dispersion compensates for the suppressed nonlinearity. The strong bidirectional power exchange dynamics are stabilized through the synergistic interplay of linear counterpropagating-wave coupling and Kerr-nonlinear cross-phase modulation. This work establishes a foundational framework for coupled soliton coexistence in monolithic microcavities, paving the way for chip-scale dual-comb spectroscopy, parallel optical processing, and reconfigurable photonic networks.