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

We present detailed statistical investigations of the irregular fast pulsin g behavior present in the dynamics of semiconductor lasers with delayed opt ical feedback operating in the low-frequency fluctuation and coherence coll apse 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 co mplementary high-resolution experimental measurement systems: a high-bandwi dth sampling digitizer and a single-shot streak camera. The experimental re sults are supported by numerical studies using the single-mode Lang-Kobayas hi equations, as well as a multimode extension of the model. Furthermore, w e also demonstrate that gain saturation and coexisting attractors can cause substantial qualitative changes of the probability density distribution.