The design of light intensity gradient trap using lithographic mask and its verification in beam pointing control application

With the advancement of phased fiber laser array technology toward more units, pointing errors between array beams have become a critical factor affecting beam combining performance. To address the challenges in fabricating light-intensity gradient trap modulation plates for beam pointing control based on light-intensity gradient traps, this paper proposes and employs a lithographic mask process to fabricate a light-intensity gradient trap modulation plate with annular stripe patterns. The measured light intensity transmittance aligns with the design value, and the root mean square error (RMSE) of the normalized transmittance is 0.0166. Through simulations and experiments, rapid correction of beam pointing errors in an extended area was achieved using the stochastic parallel gradient descent algorithm and an adaptive fiber-optics collimator. With an initial average beam pointing error of approximately 702 µrad, the mean residual pointing error after correction was reduced to less than 10 µrad. This research provides important references for laser pointing control and beam combining on extended targets.