Fig. 1. Schematic diagram of femtosecond laser processing. (a) Schematic diagram of the femtosecond laser titanium polishing device; (b) Schematic diagram of positive defocus processing; (c) Schematic of the femtosecond laser processing path

Fig. 2. Surface morphology diagrams of titanium with different processed layers. (a-d) Energy density of 25.88 J/cm² and the number of processed layers is 10, 15, 20, and 25; (e) Energy density of 18.76 J/cm² and 35 layers are processed; (f) Energy density of 11.82 J/cm²and 55 layers are processed; (g) Unprocessed surface

Fig. 3. Energy density is 25.88 J/cm², and optical microscopy and surface morphology of processed titanium with different defocusing amounts. (a) 2.6 mm; (b) 4.0 mm; (c) 4.4 mm

Fig. 4. Surface morphology diagrams of titanium processed under different defocus amounts. (a-f) Energy density is 25.88 J/cm² and the defocusing amounts are 0, 1.0, 2.0, 2.3, 2.4, and 2.5 mm, respectively; (g) Energy density is 18.76 J/cm² and defocus is 2.2 mm; (h) Energy density is 11.82 J/cm² and defocus is 1.6 mm

Fig. 5. Variation of surface morphology with different defocusing amounts at energy density of 25.88 J/cm². (a) Surface roughness variation at low defocus; (b) Etch depth variation at low defocus