Beam quality improvement for small-channel coherent beam combining with laser beams arranged along non-uniform Fermat spiral

We propose a non-uniform Fermat spiral (NFS) array for small-channel coherent beam combining. Owing to the non-uniform array density and the changing distances between two consecutive channels, the combined beam quality is naturally improved by the NFS array. All the factors affecting the combined beam quality were analyzed in detail, comparing with the hexagon array and the uniform Fermat spiral (UFS) array. Experiments were carried out to verify the combined beam quality of the small-channel optical system. It is demonstrated that the combined beam quality of the NFS array is better than that of the UFS array. The experimental results matched well with the numerical results.