Multi-dimensional wavefront manipulation of phased fiber laser array for coherent beam combining in finite-distance conformal transmission

We demonstrate the principle of generating the approximate spherical convergent light waves by wavefront manipulation for conformal transmission and coherent beam combining (CBC) based on a phased fiber laser array (PFLA) under finite transmission distance. The CBC by target-in-the-loop is investigated on the Easylaser software, revealing the theoretical relationships between the central-lobe energy of CBC and the phase manipulation method, transmission distance, and array scale. The CBC experiments are operated based on the 19element and 57-element PFLA in the 2 km real atmosphere where the clear-fringe contrast is 0.90 and 0.79, respectively, and the central-lobe energy of the CBC increased about 13.5 times and 26 times, respectively. These results validated the conformal transmission's contribution to efficient CBC and central-lobe energy increase. This work may not only present new understandings of the CBC of large-scale PFLA from the aspect of manipulating the wavefront but also provide new methods for the applications in any size of PFLA under any applying distance.