Analysis of multistability in semiconductor ring lasers

We present both an experimental and theoretical investigation of multistable states in a single-longitudinal mode and single transverse mode semiconductor ring laser (SRL). Our experiments have been performed on an InP-based multiquantum-well SRL with a racetrack geometry and a free-spectral-range of 53.6 Ghz. The power emitted from the chip is collected with a multimode fiber and detected with a 2.4 GHz photodiode connected to an oscilloscope. We show how the operation of the device can be steered to either monostable, bistable or multistable dynamical regimes in a controlled way. The diverse multistable dynamical regimes are shown to be organized in well reproducible sequences [Gelens et al., Phys. Rev. Lett. 102, 193904 (2009)]. These sequences are demonstrated to match the bifurcation diagrams of an asymptotic two-dimensional Z(2)-symmetric model for SRLs. Apart from predicting the different measured multistable time series, we demonstrate how the stochastic transitions between multistable states take place by analyzing the phase space in this model.