Spiking patterns observed at the output of lasers have been widely used to predict their dynamic behavior. The light output of a laser was associated with the coordinate of a particle moving in a potential well by Kleinman (1964). In this paper, this mechanical analogy is revisited so as to investigate a new approximation which might greatly simplify the relationships that determine the rate equations' parameters. A ruby laser numerical example is presented to highlight the consistency of the proposed approximation near the equilibrium point.