Dynamical behavior of mutually coupled semiconductor lasers: experimental investigations

Summary form only given. The study of dynamical coupling phenomena of semiconductor lasers is of great current interest and leads to new insights into the fundamental phenomena of synchronization effects and is indispensable for the realization of coherently coupled lasers. In this work, we experimentally study the dynamical behavior of two mutually coupled semiconductor lasers under moderate to strong coupling conditions. Depending on the injection current and the temperature, determining the relative frequency detuning, we have investigated the emission dynamics of both lasers. The experiments have been performed using two similar Fabry-Perot lasers placed at a distance of /spl sim/1.4 m. We have detected the intensity by a fast photodiode and analyzed it by a fast digitizing oscilloscope with 3 GHz bandwidth and an electrical spectrum analyzer. Furthermore, optical spectra with a resolution of 0.1 nm have been measured. We find chaotic low frequency fluctuations in the dynamical behavior of both lasers, exhibiting the similar features like those obtained for delayed moderate optical feedback. The dropouts of the intensity and the sub ns oscillations are identical in both lasers, but delayed to each other where the delay is /spl sim/10 ns, given by twice the propagation time between the lasers. An example of the synchronized intensity dynamics of the two lasers is depicted.