Abstract

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 Although many studies have been , carried out for laterally coupled lasers, the dynamics of mutually coupled lasers in face-to-face configuration has only been addressed recently for the weak coupling case [1]. 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 (Hitachi HLP1400) placed at a distance of ~ 1.4m We have detected the intensity by a fast photo diode 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 (LFF) in the dynamical behavior of both lasers, exhibiting the similar features like those obtained for delayed moderate optical feedback Furthermore, the dynamics of the two lasers are synchronized to each other The dropouts of the intensity and the sub-ns oscillations are identical in both lasers, but delayed to each other where the delay is ~ 10 ns, given by twice the propagation time between the lasers An example of the synchronized intensity dynamics of the two lasers is depicted in Fig 1

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