Fig. 1. Schematic diagram of the geometric relationship of laser processing lithium niobate focused beam passing through the interface

Fig. 2. Precompensation phase diagrams loaded onto the spatial light modulator. (a)‒(d) Precompensation phase diagrams at an external distance of 20 μm, 30 μm, 40 μm, and 50 μm, corresponding to a focal depth of 44 μm, 66 μm, 88 μm, and 110 μm, respectively

Fig. 3. Configuration diagram of an aberration precompensation laser processing system based on spatial light modulator

Fig. 4. Calibration of threshold energy for laser processing. (a) Variation curves of laser processing threshold energy with processing depth; (b) scanning microscopy images under different processing energies

Fig. 5. Confocal microscopic images of grating structures inside lithium niobate crystal. (a)‒(c) Side-view images at various depths, corresponding to the cases without aberration correction under high energy laser-writing, without aberration correction under threshold energy laser writing, and with aberration correction under threshold energy laser writing, respectively