Target-in-the-loop coherent beam combination of 100 W level fiber laser array based on an extended target with a scattering surface

Target-in-the-loop coherent beam combination (TIL CBC) of a 100 W level fiber laser array has been demonstrated. In the experiment, the beams from nine 10 W level fiber amplifiers achieve a scattering surface target after transmitting 10 m in free space. When the phase control system goes into close loop, atmosphere turbulence could be effectively compensated and a stable fringe pattern could be obtained on the scattering surface with 85% fringe contrast. To our best knowledge, this is the TIL CBC with the highest output power and the largest number of laser beams. Additionally, the effect of atmosphere turbulence on the backward paths on TIL CBC has been studied experimentally.