Enhanced soliton stability in bidirectionally coupled laser-microresonator systems

We investigate a bidirectionally coupled system consisting of a Kerr-nonlinear microresonator and a continuous-wave single-mode semiconductor laser. Inside the resonator, a forward-propagating and a backscattered field interact nonlinearly, while a fraction of the backscattered field is fed back into the laser cavity. We demonstrate in this paper that the interaction of the laser with the feedback opens up new ways of stabilizing solitons. Using numerical bifurcation analysis, we systematically identify existence and stability ranges of time-harmonic soliton states in the anomalous dispersion regime. We show that, in contrast with the unidirectional configuration, the bidirectional coupling introduces a dynamic self-correcting response of the laser frequency that stabilizes solitons. We further corroborate these enhanced stability properties through Monte Carlo time integrations of randomly perturbed soliton states, demonstrating a significantly larger basin of attraction for solitons in the bidirectional system, consistent with existing experimental observations.