Fig. 1. Schematic of ultraviolet micro machining system

Fig. 2. Schematics of laser machining. (a) Shock drilling; (b) rotary cutting and drilling; (c) spiral drilling

Fig. 3. SEM and 3D images of through-hole. (a) SEM image of through-hole surface; 3D images of (b) through-hole surface,

Fig. 4. SEM images of through-holes processed under different energy densities. (a) 27.68 J/cm²; (b) 29.57 J/cm²; (c) 31.12 J/cm²;

Fig. 5. Morphologies of sapphire through-holes processed under different laser repetition frequencies

Fig. 6. SEM image of drilling failure when energy density and repetition frequency of laser is 32.59 J/cm² and 45 kHz, respectively

Fig. 7. Surface morphologies of sapphire micro through-holes processed under different laser scanning speeds

Fig. 8. Cross-section SEM images and tapering angles of sapphire micro through-holes processed under different laser scanning speeds. (a) 0.9 mm/s; (b) 0.7 mm/s; (c) 0.5 mm/s; (d) 0.3 mm/s; (e) 0.1 mm/s; (f) through-hole tapering angle versus laser scanning speed

Fig. 9. Morphology image of sapphire through-hole under optimal parameter conditions. (a) SEM amplification image of through-hole edge; (b) three-dimensional image of through-hole morphology