LOW-FREQUENCY FLUCTUATIONS AND MULTIMODE OPERATION OF A SEMICONDUCTOR-LASER WITH OPTICAL FEEDBACK

We experimentally investigate low frequency fluctuations (LFF) in a Fa bry-Perot semiconductor laser with optical feedback from an external m irror. During LFF, the time resolved optical spectrum shows that many longitudinal modes of the solitary laser enter into the transients. Af ter each LFF event, the excited solitary-laser modes recover similarly . However, the recovery for the power in each mode is much slower than the recovery of the total power. The intermode exchange of energy dur ing the recovery indicates that a single-longitudinal mode description of such LFF behavior will not capture important underlying dynamics. The relevance of multimode dynamics is confirmed in a feedback experim ent where the external mirror is substituted by a diffraction grating. (C) 1998 Elsevier Science B.V.