The simulation software SEMSIS, which was developed at Fraunhofer ILT, allows multiphysics modeling of edge-emitting lasers and VCSELs considering their electrical, optical, thermal and mechanical properties in a self-consistent manner. Special use-cases include the prediction of the lateral emission characteristics of broad-area emitters and the computation of threshold values for catastrophic optical damage (COD) of edge-emitting lasers under external optical feedback.