Dynamics and stability conditions of a spectrally combined beam based on a diode laser array

Abstract

In the spectral beam combining (SBC) system based on a diode laser array (DLA), optical feedback is required to lock the wavelengths of the diode lasers, but excessive feedback may lead to instability. To analyze the dynamics and stability conditions of the SBC system based on DLA, a model for the round-trip propagation of the feedback beam in the external cavity is established, and the optical feedback is calculated using the diffraction integral method. On this basis, a stability condition (the feedback-factor is smaller than 0.07) is introduced to assess the potential stability of the SBC system. If the feedback-factor exceeds 0.07, the combined laser can be in chaos. Based on the stability condition, we analyzed the influence of external-cavity parameters on the external-cavity feedback. The results indicate that the optical feedback becomes increasingly strong with the increasing focal length of the transform lens and the reflectivity of the output coupler, while it decreases with the increasing reflectivity of the front facet of the diode emitter. This work paves the way toward the stabilized spectral beam combining system based on a diode laser array.