Picosecond intensity statistics of semiconductor lasers operating in the low-frequency fluctuation regime

We present detailed statistical investigations of the irregular fast pulsing behavior present in the dynamics of semiconductor lasers with delayed optical feedback operating in the low-frequency fluctuation and coherence collapse regimes. We demonstrate that the probability density distributions of the laser intensity on a picosecond time scale are essentially independent of the number of optical modes involved in the laser emission, using two complementary high-resolution experimental measurement systems: a high-bandwidth sampling digitizer and a single-shot streak camera. The experimental results are supported by numerical studies using the single-mode Lang-Kobayashi equations, as well as a multimode extension of the model. Furthermore, we also demonstrate that gain saturation and coexisting attractors can cause substantial qualitative changes of the probability density distribution.