Fig. 1. Diagram of laser drilling method^[4]

Fig. 2. Schematic diagram of the machining system

Fig. 3. Schematic diagram of the spiral scan path

Fig. 4. Schematic diagram of the flow test apparatus

Fig. 5. Physical mode

Fig. 6. Curve of square of the hole diameter versus water flow

Fig. 7. Representation of taper

Fig. 8. Curve of taper versus water flow

Fig. 9. Curve of circular degree versus water flow

Fig. 10. Curve of hole depth versus water flow

Fig. 11. Comparison of two-dimensional morphology of hole walls.(a) With vertical stripes; (b) Without vertical stripes

Fig. 12. Three-dimensional morphology and roughness curve of the internal wall of the microhole

Fig. 13. Effect of single pulse energy on entrance and exit diameter and taper

Fig. 14. Effect of single layer scanning time on entrance and exit diameter and taper

Fig. 15. Effect of single layer feed on entrance and exit diameter and taper

Fig. 16. Two-dimensional morphology of microporous surface. (a) En-trance; (b) Exit