Fig. 1. Schematic illustration of the experimental setup. HWP, half-wave plate; GTP, Glan–Taylor polarizer; L1, convex lens of focal length 50 cm; LN, lithium niobate; PC, personal computer.

Fig. 2. SEM images of a fs laser processed LN surface in N2 environment with sample temperature of (a) 28°C, (b) 100°C, (c) 200°C, (d) 300°C, (e) 400°C, (f) 500°C, (g) 600°C, and (h) 800°C, respectively. Fluence, 7.0  kJ/m2; N2 pressure, 500 Torr; scanning speed, 2 mm/s. The red double arrow indicates the direction of polarization of the incident laser.

Fig. 3. (a) Absorption spectra of fs laser processed LN; (b) absorption at 800 nm dependence of LN processed under the different temperatures. All samples were fabricated with the fluence of 7.0  kJ/m2 at 2 mm/s scanning speed, 500 Torr N2 pressure, and the temperatures of 28°C, 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, and 800°C, respectively.

Fig. 4. SEM images of the periodic surface structures formed by the irradiation of a linearly polarized laser under the sample temperature of 500°C. Fluences: (a) 5.0, (b) 6.0, (c) 7.0, (d) 8.0  kJ/m2, respectively. The red double arrow indicates the direction of polarization of the incident laser.