The well-known alpha-factor is a convenient measure to describe the magnitude of the amplitude-phase coupling of semiconductor lasers. But is the alpha-factor really a parameter? First-principle simulations of InGaAs quantum-dot lasers and amplifiers show that in spatially extended quantum-dot laser structures, the amplitude phase coupling is far from being a constant. Our computation of the alpha-factor demonstrates the same large and excitation-dependent variation and scatter as corresponding to experimentally determined values. Our results therefore provide a key to the interpretation and give a measure of applicability of the alpha-factor for the classification of quantum-dot lasers. (c) 2005 American Institute of Physics.