  Optical Frequency Comb (OFC) generated by semiconductor lasers are currently
widely used in the extremely timely field of high capacity optical
interconnects and high precision spectroscopy. Very recently, several
experimental evidences of spontaneous OFC generation have been reported in
single section Quantum Dot (QD) lasers. Here we provide a physical
understanding of these self-organization phenomena by simulating the multi-mode
dynamics of a single section Fabry-Perot (FP) QD laser using a Time-Domain
Traveling-Wave (TDTW) model that properly accounts for coherent
radiation-matter interaction in the semiconductor active medium and includes
the carrier grating generated by the optical standing wave pattern in the laser
cavity. We show that the latter is the fundamental physical effect at the
origin of the multi-mode spectrum appearing just above threshold. A
self-mode-locking regime associated with the emission of OFC is achieved for
higher bias currents and ascribed to nonlinear phase sensitive effects as Four
Wave Mixing (FWM). Our results are in very good agreement with the experimental
ones.
