Figure 4: Different regimes of nonlinearity-induced mode splitting.
From: Symmetry Breaking of Counter-Propagating Light in a Nonlinear Resonator
(a) Theoretical prediction for the power PCW coupled into the resonator in the clockwise direction as a function of the normalised laser detuning frequency δ/γ. The incident power imbalance is colour-coded with red (blue) contours corresponding to higher power in the CW (CCW) direction. The bold black curve shows spontaneous symmetry breaking in the case of equal pump powers. In this region between the two grey lines, two stable solutions exist for a range of power imbalances. The beige shaded area contains unstable solutions. (b) Scan of the laser frequency across the resonance while backscattering-induced interference effects in the setup cause Pin, CCW/Pin, CW to change about unity by ±3% at a period of ~170 MHz in the laser frequency. The launched power is 180 mW in each direction. Outside the grey lines the coupled power difference is enhanced with respect to the incident power imbalance by the non-reciprocal Kerr shift. The enhancement increases approaching the bistable regime, in which the system begins to jump between the two stable configurations. The inset shows a sweep across a microresonator mode with equal power and no interference effects, leading to a “bubble”-shaped symmetry-broken region corresponding to the bold black trace in panel (a).
