Adaptive modulation of femtosecond laser multi-beams based on hologram design and feedback loop

Femtosecond lasers demonstrate unique advantages in micro/nano processing and are widely used in precision manufacturing. However, the inherent Gaussian intensity distribution of single-beam fundamentally limits processing efficiency, while multi-beam approaches suffer from energy non-uniformity due to phase distortions and optical aberrations. To address these challenges, this study proposes a multi-beam energy uniformity enhancement method based on hologram design (by optimizing the weighting of superimposed holograms) and real-time feedback loop (dynamically correcting the impact of light source deformation and hardware defects on beam quality). Experimental findings clearly show the proposed approach successfully accomplishes uniform four-beam modulation, enabling a four-times increase in processing speed. When only the proposed hologram design method is used, the uniformity factor of four beam is 0.831, and the standard deviation of the intensity ratio of four beams is 2.3 %. When the hologram design is combined with the correction of the feedback loop, the uniformity factor increases to 0.965 and the standard deviation is reduced to 0.4 %. In actual processing, the uniformity of the ablation width reaches 6.10 ± 0.426 μm. The proposed method can both improve the processing efficiency and enhance the processing quality, which provides a new technological approach for the application of femtosecond laser processing.