Fig. 1. Schematic diagram of femtosecond laser processing. (a) Schematic diagram of LIPSS in the PMN-PT crystal by femtosecond laser direct writing, the red arrow represents the direction of laser scanning, the blue arrow represents the direction of polarization of the laser; (b) Schematic diagram of the femtosecond laser-induced LIPSS

Fig. 2. Morphology of SWPSS induced by femtosecond laser. (a)~(c) SWPSS at velocities of 5 mm/s, 3 mm/s, and 2 mm/s respectively

Fig. 3. (a) Morphology of the LSFL with velocities of 0.7 mm/s, 0.8 mm/s, and 0.9 mm/s respectively; (b) Period of LIPSS in relation to laser parameters

Fig. 4. (a) Raman spectra of the LIPSS with the variation of temperature, the inset shows the variation of the Raman spectra at the Raman shift near the 50 cm⁻¹ ; (b) Intensity of Raman signal of the PMN-PT crystal with the variation of temperature; (c) Intensity of Raman signal of the LIPSS with the variation of temperature