Statistical Properties of an External-Cavity Semiconductor Laser: Experiment and Theory

We experimentally and numerically study the statistical properties of a semiconductor laser with time-delayed optical feedback. Our systematic analyses show that the statistical distribution of the raw intensity obtained from experiments is better fitted by a Laplacian distribution; both in experiments and simulations, the distribution pattern of the differential signal obtained from two independent intensities, as well as of that computed from its high-order finite differences, converges to a well-fitted Gaussian profile for high pump currents. This helps us to understand the changes in statistical properties of the intensity with varying control parameters and achieve desired entropy sources for random number generators. Furthermore, in numerical simulations, we find the distribution of the differential signal undergoes a marked transition from a Gaussian to Laplacian profile as the feedback rate increases at low to moderate pump currents.