Polarization chaos from a free-running quantum dot laser diode

For fifty years semiconductor lasers have been considered as damped nonlinear oscillators, thus they could not be driven into chaos unless one uses external forcing, e.g. optical feedback or parameter modulation. Here we demonstrate experimentally the generation of polarization chaos in a free-running vertical-cavity surface-emitting laser (VCSEL), i.e. chaotic mode mode hopping between two polarization modes [1], and provide the theoretical bifurcation scenario leading to chaos in the framework of the spin-flip model (SFM) [2].