Fig. 1. Schematic of generation of periodic microstructures on surface of Ti induced by femtosecond laser

Fig. 2. SEM images of microstructures on surface of Ti under line-scanning at different laser fluences when effective-pulse number per unit point is 40. (a) 11.30 J·cm-1; (b) 10.17 J·cm-1; (c) 9.04 J·cm-1; (d) 7.91 J·cm-1; (e) 6.78 J·cm-1; (f) 5.65 J·cm-1; (g) 3.39 J·cm-1; (h) 1.13 J·cm-1; (i) 0.68 J·cm-1; (j) 0.23 J·cm-1

Fig. 3. Squared width of ablated zone as a function of laser fluence when effective-pulse numbers per unit point are 10, 40, and 100, respectively

Fig. 4. SEM images of microstructures on surface of Ti induced by different scanning times when laser fluence is 1.13 J/cm2. (a) 1; (b) 2; (c) 4; (d) 8; (e) 10; (f) 20; (g) 40; (g) 80

Fig. 5. Height of femtosecond laser-induced microstructure on surface of Ti as a function of scanning time, when laser fluence is 1.13 J/cm2

Fig. 6. SEM images of microstructures on surface of Ti induced by different scanning times when laser fluence is 5.56 J/cm2. (a) 1; (b) 5; (c) 8; (d) 10; (e) 20; (f) 40

Fig. 7. SEM images of microstructures on surface of Ti induced by different scanning times when laser fluence is 10.17 J/cm2. (a) 1; (b) 5; (c) 10; (d) 20

Fig. 8. SEM images of microstructures on surface of Ti at different scanning speeds and different laser fluences when scanning pitch is 20 μm

Fig. 9. Effects of laser fluence and scanning speed. (a) Schematic of fluence distribution of Gaussian laser beam; (b) schematic of spot overlapping at different scanning speeds and fluences in parallel scan

Fig. 10. SEM images of microstructures on surface of Ti at different scanning pitches and scanning times

Fig. 11. SEM images of microstructures on surface of Ti at different effective-pulse numbers (1000, 1500, and 2000) when laser fluence is 1.13 J/cm2. (a)-(c) 1000; (d)-(f) 1500; (g)-(i) 2000n

Fig. 12. SEM images of microstructures on surface of Ti at different laser fluences and effective-pulse numbers