Active tip/tilt aberration compensation technique for fiber laser array based on optical window feedback

In a beam combining system of fiber laser array, it is generally necessary to maintain all beams parallel. An active tip/tilt aberration compensation technique based on optical window feedback is proposed in this paper. A high-transmittance optical window is positioned at the exit of the fiber laser array as an optical sampler, allowing the majority of the laser to pass through while a small portion is reflected back. The reflected laser returns to the fiber along the original optical path, and is used as an evaluation function to control all beams to be perpendicular to the optical window. In this way, all beams will remain parallel. By implementing a parallel control strategy, the control speed of the system is faster and less affected by the number of beams. In the optical path, all devices except the optical window can use the fiber devices, making the system more compact and stable. Finally, a tip/tilt aberration compensation experiment of 19-channel fiber laser array has been developed using the above technique. In the experiment, a convex lens is used to focus the beam array, and the light spots on the focal plane almost coincide, which indicates that all beams remain parallel.