Multistable and excitable behavior in semiconductor ring lasers with broken Z(2)-symmetry

We study the bifurcation scenario and the evolution of the counter-propagating modes in a semiconductor ring laser when their symmetry is broken. We show how a two-dimensional asymptotic model for this asymmetric ring laser can be used to interpret and predict regions of multistability and excitability in the laser. The theoretical predictions and insights in these different dynamical regimes of the asymmetric semiconductor ring laser are confirmed and further explored experimentally in a semiconductor ring laser set-up that allows to controllably break the Z(2)-symmetry of the laser.