Influence of coherent coupling between counterpropagating waves on spontaneous symmetry breaking and complex oscillations in Kerr microcavities

We theoretically study the impact of coherent intermode coupling on the nonlinear dynamics of two counterpropagating modes in a Kerr microcavity driven by symmetric counterpropagating pumps, focusing on the realization of stationary and oscillatory states with broken symmetry. Notably, the symmetry-breaking threshold for positive intermode coupling coefficients β grows sharply, while for negative β the threshold first decreases, reaches a minimum, and then gradually increases as |β| increases. We show that the system exhibits robust and self-similar behavior with symmetry breaking and symmetry restoring in stationary regimes for a fairly wide range of negative β and pump powers. The model with real positive and negative β covers all possible cases in which spontaneous symmetry breaking can occur. We also demonstrate that diverse oscillatory regimes are observable only within a very narrow range of small |β| and these regimes are highly sensitive to β. Therefore, when utilizing oscillatory regimes, even weak intermode coupling should not be neglected and requires careful attention. These findings have applications in the development of ultrasensitive miniature sensors, as well as other devices employing spontaneous symmetry breaking.