Interaction-induced mode switching and threshold condensation in steady-state microlasers

In this talk we discuss two novel effects in steady state microlasers. The first one is interaction-induced mode switching (IMS), where the onset of a new lasing mode switches off an existing mode via a negative power slope. It's a deterministic effect in steady state lasing and caused by cross saturation of the gain medium, hence it's different from dynamic mode switching or hopping. For a fixed pump profile, a simple analytic criterion for the occurrence of IMS is given in terms of their self- and cross-interaction coefficients and non-interacting thresholds, which is verified for the example of a two-dimensional microdisk laser. When the spatial pump profile is varied as the pump power is increased, IMS can be induced even when it would not occur with a fixed pump profile, as we show for two coupled laser cavities.