  The aim of this paper is to review some of the models and solution techniques
used in the simulation of high-power semiconductor lasers and to address open
questions. We discuss some of the peculiarities in the description of the
optical field of wide-aperture lasers. As an example, the role of the substrate
as a competing waveguide in GaAs-based lasers is studied. The governing
equations for the investigation of modal instabilities and filamentation
effects are presented and the impact of the thermal-lensing effect on the
spatiotemporal behavior of the optical field is demonstrated. We reveal the
factors that limit the output power at very high injecton currents based on a
numerical solution of the thermodynamic based drift-diffusion equations and
elucidate the role of longitudinal spatial holeburning.
