We analyse the sensitivity of quantum dot semiconductor lasers to optical feedback. While bulk and quantum well semiconductor lasers are usually extremely unstable when submitted to back reflection, quantum dot semiconductor lasers exhibit a reduced sensitivity. Using a rate equation approach, we show that this behaviour is the result of a relatively low but nonzero line-width enhancement factor and strongly damped relaxation oscillations.

The response of an optically injected quantum dot semiconductor laser is studied both experimentally and theoretically. Specifically, the locking boundaries are investigated, revealing features more commonly associated with Class A lasers rather than conventional Class B semiconductor lasers (SLs). Further, various dynamical regimes are observed including excitability and multistability. Of particular interest is the observation of a phase-locked bistability. We determine the stability diagram analytically using appropriate rate equations for quantum dot lasers. In particular, the saddle-node (SN) and Hopf bifurcations forming the locking boundaries are examined and are shown to reproduce the observed experimental stability features. The generation of the phase-locked bistability is also explained via a combination of these bifurcations.

We analyse theoretically and experimentally the residence time distribution of bistable systems in the presence of noise and time-delayed feedback. The feedback provides a memory mechanism for the system which leads to non-Markovian dynamics. We demonstrate and explain various non-exponential features of the residence time distribution using a two-state as well as a continuous model. The experimental results are based on a Schmitt Trigger where the feedback is provided by a computer generated delay loop and on a semiconductor laser with opto-electronic feedback.

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