Abstract
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 will demonstrate that the sideband approach (originally proposed by Casperson,1 and readjusted by Hendow and Sargent2 in order to account for the buildup of two symmetric side-modes in the laser spectrum, along with the oscillating mode) is insufficient to explain the distortion that occurs in the (initially) Gaussian profile when the output field undergoes large departures from stable operation. This report focuses on both numerical and analytical handling of the integro-differential ‘Maxwell-Bloch’ equations. An original approach, presented here 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 fan effect that has always been ignored in the treatment of SMIB laser dynamics).1,2 We will show that lateral holeburning cannot be described with the usual small-sideband analysis. In addition, we will 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 fieldswitching around a zero mean-value, we will derive analytical expressions that give a remarkably good account of the dynamic profiles, obtained likewise by numerical integration of the integro-differential equations. These findings give further credit to the simple models of SMIB laser dynamics,3 since the active velocity components are located in a self-consistent manner. Furthermore, the presented results confirm experimental reports on a regime where two side-frequencies dominate the output power spectrum.4
© 1999 Optical Society of America
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