Comparative study of some travelling-wave semiconductor laser amplifier models

Mathematical models for travelling-wave semiconductor laser amplifiers are compared in the steady state for a simplified case where the exact solution is easily obtained. The frequently used model with the photon density averaged over the length of the amplifier is examined together with a simple perturbation model and a new orthogonal function model. The photon density averaging model is the most accurate. The perturbation model is less reliable because of its simplifications. For the orthogonal function model, the complexity grows much faster than the accuracy and therefore this model is unpractical.