A key challenge in designing a spectral beam combining (SBC) system based on a diode laser array (DLA) is how to avoid excessive optical feedback induced by the diffraction grating in the system. Optical feedback introduced into individual laser elements in the array may cause unwanted instabilities in the lasers’ output, leading to poor beam quality. To tackle this challenge, the authors of this paper explore theoretically the impact of optical feedback in the DLA-based SBC system using, where possible, experimental parameters. The results show that the diversity of dynamics available from the lasers is high and their output follows a well-defined route to deterministically chaotic output. Further analysis gives the stability region described by the key system parameters including feedback factor, focal length of the transform lens, reflectivity of the output coupler and the reflectivity of the front facet of the diode laser. The findings presented in this paper provide practical guidelines for the design of a high brightness and good beam quality DLA-based SBC system.

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