Fig. 1. The real space definition and schematic diagram of polarization adjustment. (a) The real space definition of x-cut LN; (b) schematic diagram of polarization adjustment

Fig. 2. Optical tomography images of ablation results of single pulse femtosecond laser irradiation on LN at different energy densities and four polarized directions

Fig. 3. Confocal scanning of single pulse irradiation with different polarizations. (a) 0° polarization; (b) 45° polarization; (c) 90° polarization; (d) 135° polarization (red arrow indicates polarization direction)

Fig. 4. SEM images of the surface irradiated by laser irradiation of under four polarization directions. (a) 0.95 J/cm²; (b) 9.01 J/cm²

Fig. 5. Fitting diagrams of the damage threshold under different polarizations. (a) Enlargement near the fitting threshold; (b) the red is the fitting line, and the blue is the change of the depth of the ablation hole

Fig. 6. The PDOS and atomic rod like pattern of LN crystals, as well as the matching relationship between bond angle and laser polarization direction. (a) PDOS; (b) stick chart and matching relationship between key angle and laser polarization direction