Circuit modeling of the effect of diffusion on damping in a narrow-stripe semiconductor laser

This paper describes a circuit modeling technique for directly modulated narrow-stripe semiconductor lasers with strong carrier confinement and index guiding. It is shown that diffusion damping of the modulation response, due to a nonuniform electron density distribution in the active layer, can be accounted for in terms of an equivalent optical gain saturation. Based on this equivalence, a small-signal ac circuit model of a narrow-stripe laser is derived. The model can be used to determine the intensity modulation and frequency modulation response characteristics of a packaged device.