Fast-Fourier-transform based beam-propagation model for stripe-geometry semiconductor lasers: Inclusion of axial effects

Abstract

The static characteristics of gain-guided double-heterostructure semiconductor lasers are modeled using a beam-propagation method that is capable of including both the axial and lateral variations of the optical-mode and carrier-density profiles. The use of the fast-Fourier-transform algorithm for the lateral mode propagation results in a relatively fast numerical procedure to obtain the self-consistent solution of the wave equation coupled to a nonlinear carrier-diffusion equation. To compare it with previous work, the model is applied to study the above-threshold behavior of an axially uniform AlGaAs laser. The inclusion of axial effects leads to minor (∼few percent) quantitative changes. As a novel application of the beam-propagation model, a tapered-stripe AlGaAs laser is analyzed in detail. In this axially nonuniform device the lateral profiles for the carrier density and the forward and backward waves exhibit considerable axial variations and affect the behavior both qualitatively and quantitatively. The calculated results are in reasonable agreement with the reported experimental observations.