Spatial inhomogeneity of inversion and undamped pulsations of solid-state lasers

An analogy is suggested between the emission of radiation from a solid-state laser and the frictional motion of a particle in a potential well. This analogy is used to demonstrate analytically that a system of rate equations which allows only for the spatial inhomogeneity of the population inversion fails to describe the undamped pulsation regime. It is shown that this inhomogeneity makes the emission much more sensitive to perturbations in a real resonator. A comparison of the theoretical and experimental results is used to demonstrate the existence of a mechanism which generates undamped pulsations but is not related to laser instabilites.