Dynamic gain profiling in self-pulsing lasers

Summary form only given. Despite the large number of reports that were devoted to the investigation of the dynamic properties of single-mode inhomogeneously broadened (SMIB) lasers, some of their operative characteristics still demand further investigation. In connection with physical understanding of laser instabilities, we demonstrate that the sideband approach is insufficient to explain the distortion that occurs in the (initially) Gaussian profile when the output field undergoes large departures from stable operation. The report focuses on both numerical and analytical handling of the integro-differential ´Maxwell-Bloch´ equations. An original approach, presented for the first time, consists in tracking the gain contour when a self-pulsing regime sets in. We demonstrate the occurrence of a lateral hole-burning effect that has never been revealed before. These findings lend themselves to the recognition of the fact that the unstable state initiates lateral saturation (an effect that has always been ignored in the treatment of SMIB laser dynamics). We show that lateral hole-burning cannot be described with the usual small-sideband analysis. In addition, we prove that, to first order, the role of population pulsations is masked by a DC component, distinct from the steady-state value, and responsible for the gain distortion. Leaning on obvious hints related to the occurrence of an amplitude field-switching around a zero mean-value, we derive analytical expressions that give a remarkably good account of the dynamic profiles, obtained likewise by numerical integration of the integro-differential equations.