A CONTRIBUTION BASED ON CIRCUIT MODELING TO STUDY THE EFFECT OF NONLINEAR GAIN ON HIGH-FREQUENCY CHARACTERISTICS OF SEMICONDUCTOR-LASERS

The high-frequency characteristics of semiconductor lasers are describ ed using an equivalent circuit model. The paper investigates the small -signal intensity modulation (IM) and frequency modulation (FM) when t he parabolic gain approximation is used and when lateral diffusion of carriers in the active region of the laser is taken into account via a one-dimensional diffusion equation. We have performed the small-signa l analysis to give a more transparent description of the influence of parabolic gain approximation on the modulation response. The inclusion of parabolic gain approximation and the gain compression characterist ics of the active region in the expression derived for IM, FM and the chirp-to-modulated power ratio allows the present model to reflect the influence of the laser structure on the modulation performances.