Transition between turbulent regimes in a forced semiconductor laser

This paper presents an experimental observation of the transition between different turbulent behaviors of a strongly multimode semiconductor laser with external optical forcing. The optical phase is resolved and the formation of defects in relation to the statistical properties of the field is characterized. Our experimental setup is composed by a semiconductor laser in a Fabry-Perot configuration (slave laser) which is forced by a external field provided by a grating tunable edge-emitting laser (master laser). Two types of measurements were performed. The first one is a spatiotemporal digram where the horizontal axis is equivalent to space inside the cavity and the vertical dimension describes the evolution in units of roundtrip. The second one is a phase measurement which requires the implementation of a heterodyne-like technique. Thanks to the reconstruction of the power fluctuations and the relative phase, we can analyse in function of the power of the external forcing and the detuning between the slave and the master laser in which kind of turbulent or non-turbulent state the laser is. A different localized events with a high amplitude and with a weak probability of appearance can be observed well above threshold of the slave laser, with a high detuning but a high power of the master laser. Whereas if the detuning is decreased the dynamics is totally different and we observe different kind of defects in a turbulent-like regime.