Spectrally combining beam degradation caused by DLA defects: modeling and analysis

The paper investigates the degradation of beam quality in spectral beam combining (SBC) systems with dual-gratings caused by defects in diode laser arrays (DLAs), focusing on the combined effects of beam linewidth, divergence angle, and beam deflection. A comprehensive model is developed to analyze how these defects affect the wavelength-locking mechanism and beam propagation, thereby degrading the output beam characteristics. The results reveal that the dual-grating configuration effectively mitigates angular broadening induced by linewidth dispersion. A linewidth of 1 nm results in a mere 8% reduction in the peak intensity of the combined beam, concomitantly leading to a 0.5 increase in the β factor. Although beam divergence exacerbates the degradation of beam quality, beam deflection is the dominant factor. A deflection angle of 3 mrad results in a 38% reduction in peak intensity and a 2.6 increase in the β factor, underscoring the necessity of controlling beam deflection. We hope this work provides critical insights into the interplay between DLA imperfections and SBC performance, offering a theoretical foundation for optimizing high-power, near-diffraction-limited beam combining systems.