We analyze multi-longitudinal-mode semiconductor lasers experimentally. We show that the intensity of each mode displays large amplitude oscillations but obeys a highly organized antiphase dynamics leading to an almost constant total intensity output. For each mode, regular switching is observed in the megahertz range, while the optical frequency as a function of time follows a well defined sequence from blue to red. Using a multimode theoretical model, we identify that four-wave mixing is the dominant mechanism at the origin of the observed dynamics. The asymmetry of the susceptibility function of semiconductor materials allows us to explain the optical frequency sequence.

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We report on experimental observations of homoclinic snaking in a vertical-cavity semiconductor optical amplifier. Our observations in a quasi-one-dimensional and two-dimensional configurations agree qualitatively well with what is expected from recent theoretical and numerical studies. In particular, we show the bifurcation sequence leading to a snaking bifurcation diagram linking single localized states to "localized patterns" or clusters of localized states and demonstrate a parameter region where cluster states are inhibited.

Cavity solitons in semiconductor amplifiers were, from the beginning of their study and observation, obtained either spontaneously or in a controlled manner by local coherent excitation. We describe two experiments that demonstrate coherent and, we believe for the first time, incoherent writing and erasure of cavity solitons in an optically pumped vertical-cavity semiconductor amplifier by short optical pulses.

In this paper, we experimentally analyze the modal dynamics of quantum-well semiconductor lasers. Modal switching is the dominant feature for semiconductor lasers that exhibit two or several active longitudinal modes in their time-averaged optical spectrum. In quantum-well lasers, these dynamics involve a periodic switching among several longitudinal modes, which follows a well-determined sequence from the bluest to the reddest mode in the optical spectrum. This feature is radically different from the well-known noise-driven mode-hopping occurring in bulk lasers which involves only two main modes. We analyze the differences in modal dynamics for these two kinds of laser by comparing the modal switching statistics and by studying the effects of noise and modulation in the pumping current