Comparison of spectral beam combining characteristic based on plane and concave gratings

A spectral beam combining (SBC) system by using a concave blazed grating with a Rowland-circle mount with the radius of 0.2 m was firstly built by us. Theoretically, on the basis of 5-element fiber lasers, the combining result for a plane and concave blazed grating optimized by using the recursive method were compared. The result shows that the energy density (ED) for the concave grating at the focus point is far higher than that for the plane grating, the beam quality for the concave grating is slightly inferior than that for the plane grating. Experimentally, two lasers with the wavelengths of 1544.6 nm and 1561.2 nm were combined. For the plane grating, at a point 153 mm form the grating, the measured ED was 2.07 mW/mm2 with the beam quality factor(M2) of 1.28. While for the concave grating, the measured ED at the same position was 691.2 mW/mm2 with M2 of 1.92. The simulation and experiment results indicate that SBC using a concave grating due to its higher ED has more advantages in directed-energy applications such as defense and manufacturing.