Fig. 1. Laser scanning process and diffraction principle

Fig. 2. Initial parameters when iris effect appears during laser scanning.(a) At different intervals; (b) at different laser repetition frequencies

Fig. 3. Micrographs under different energy percentages at scanning speed of 400 mm/s, repetition rate of 20 kHz, and scanning interval of 0.02 mm. (a) 55%; (b) 57%; (c) 59%; (d) 61%; (e) 63 %; (f) 65%

Fig. 4. Micrographs under different laser scanning intervals at scanning speed of 400 mm/s, repetition rate of 20 kHz, and energy percentage of 80%. (a) 0.04 mm; (b) 0.05 mm; (c) 0.06 mm; (d) 0.07 mm

Fig. 5. Generation process of iris on stainless steel surface induced by laser. (a)‒(c) Process of laser influence on stainless steel surface; (d) generation principle of iris

Fig. 6. Effect of pattern iris prepared by laser. (a)(b) Vertical iris effects; (c)(d) horizontal iris effects; (e)(f) normal overhead views;

Fig. 7. Laser induced composite structural colors of stainless steel. (a)‒(d) Color produced by oxide film; (e)‒(h) iris structural colors of Fig.7(d) produced at different inclined angles; (i) microstructure of Fig.7(d)