Analysis of beam characteristic in the single and dual grating spectral beam combining of fiber laser array with pointing deviation

As a basis of evaluating output laser performance, maintaining excellent beam quality is of great importance for the construction of the spectral beam combining (SBC) system. The influence of pointing deviation on the beam characteristic is studied in SBC of different technical solutions theoretically. The incident light field of the fiber laser array with the pointing deviation is derived by the transformation of coordinates, and the change of the combined beam quality with normal distributed random perturbations is discussed by the principle of beam diffraction and the statistical analysis. When the pointing deviation of the laser array is only 0.5 mrad, the beam quality factor of the SBC system will increase to (2.80±0.68) for the single grating SBC and (4.10±1.29) for the dual grating SBC. It can be concluded that the pointing deviation has a significant effect on the beam characteristics of the SBC systems. Compared with the single grating SBC, the dual grating scheme is more sensitive to pointing deviation.