Precise measurements and computer simulations of mode‐hopping phenomena in semiconductor lasers

We precisely measured temporal intensity variations of each longitudinal mode of a two‐mode 1.5‐μm InGaAsP laser. The intensities of these modes showed clear hopping between each other. It became clear for the first time that their power spectral densities represented typical Lorentzian with a cut‐off frequency between 0.7 and 1.9 MHz. This means that mode hopping follows the stochastics of a Poisson process, i.e., it occurs completely at random in time. The results of analog computer simulation, using a detailed theoretical model, supported the experimental results. It is concluded that spontaneous emission acts as a trigger to this hopping.