ANDRONOV BIFURCATION AND EXCITABILITY IN SEMICONDUCTOR-LASERS WITH OPTICAL FEEDBACK

We experimentally investigate the dynamical behavior of a semiconducto r laser with optical feedback. We show that noise plays an important r ole close to the instability threshold, while determinism controls the so-called coherence collapse regime. We identify the bifurcation whic h is at the origin of the low frequency fluctuations. It is the result of a collision between a stable fixed point and a saddle point (Andro nov's bifurcation). We provide experimental proof that the laser with optical feedback behaves as an excitable medium.