Decoupling and control of sub-beam pointing in fiber laser arrays based on differential energy detection

Correcting tip-tilt aberrations is essential for improving beam-combination performance on the target plane in laser-array systems. In a multi-beam system, however, the correspondence between each tip-tilt corrector and its target-plane spot is generally unknown, making it difficult to apply a control signal directly to the appropriate corrector. Existing tip-tilt correction methods therefore rely largely on iterative optimization, which often requires many iterations when the initial aberration is large and consequently limits correction speed. This paper proposes a differential-energy-detection-based method for decoupling and controlling the pointing of sub-beams in a laser array. First, the positions of multiple target-plane sub-spots are extracted and indexed, and the tip-tilt aberration of each sub-beam is obtained from the deviation between its spot position and the target position. Small perturbations are then applied sequentially to the tip-tilt correctors. A differential energy map is constructed from each perturbed image and the reference image, and the local residual energy is measured around every indexed spot. This process establishes a one-to-one correspondence between the sub-spots and the correctors and thereby decouples sub-beam pointing. Using a pre-calibrated control model, the tip-tilt aberration of each sub-beam is converted into the corresponding control voltage and applied to the matched corrector, enabling rapid correction of large tip-tilt aberrations. Numerical simulations and experiments show that the proposed method reliably establishes the spot-to-corrector mapping and rapidly reduces large tip-tilt aberrations.