Numerical Treatment of Boundary Conditions to Reduce High-Frequency Artifacts in Simulations of Distributed-Feedback Lasers

High-frequency artifacts may occur when the coupled-mode equations describing distributed-feedback lasers are solved by a variety of numerical methods, such as method-of-characteristics schemes and the split-step method. We propose a simple technique to suppress this artifact. Its idea is to modify the numerical implementation of the boundary conditions to promote the leakage of highest-frequency modes out of the medium. At the same time, this implementation only minimally affects the physical part of the solution. We demonstrate the effectiveness of this technique for first- and second-order schemes.