Self-consistent modeling of beam instabilities in 980-nm fiber pump-lasers

Emission nonlinearities such as kinks in the L-I characteristic and beam steering have often been observed in semiconductor power lasers that were designed for single-mode operation. A physical model of these phenomena is presented in which they are attributed to effects of the lasing and coherent coupling of multiple lateral modes. This model has been implemented self-consistently in a finite-element scheme. Simulation results for a typical 980-nm fiber pump laser are described and are found to be in good qualitative agreement with experimental observations. This agreement includes bilateral steering of the peak field, nonsymmetric emission field intensity in a symmetric device, nonlinearity and kinks in the L-I characteristics, and beating patterns in the back plane image.