Fig. 1. Evaluation on dimension and morphological characteristics of laser ablated micro-hole. (a) Dimension characteristics; (b) morphological characteristics

Fig. 2. Laser processed hole cracks. (a) Trend diagram of single hole crack morphology^[21]; (b) single hole cracks on aluminum oxide ceramics processed by millisecond laser^[22]; (c) trend diagram of group hole crack morphology^[23]; (d) group hole cracks on aluminum oxide ceramics processed by nanosecond laser^[24]

Fig. 3. Millisecond laser processed holes on silicon carbide ceramics ^[30]. (a) Effect of scanning speed on hole circularity；(b) SEM images of inlet; (c) SEM images of outlet

Fig. 4. Millisecond laser processed holes on aluminum oxide ceramics in air and liquid. (a) Inlet/outlet circularity of hole for laser processing in air, water and salt solution ^[31]; (b) effect of optical length in liquid on inlet/outlet roundness of hole ^[31]; (c) schematic of laser processing assisted by liquid ^[32]

Fig. 5. Inlet images of millisecond laser processed holes on aluminum oxide ceramics. (a) Effect of pulse duration on inlet melting material^[33]; (b) effect of laser power on inlet melting material^[33]; (c) effect of repetition rate on inlet melting material^[34]

Fig. 6. Millisecond laser processed holes on aluminum oxide ceramics. (a)(b) Effect of peak power on inlet spatters^[36]; (c) effect of pulse duration on inlet spatters^[36]; (d) inlet surface for laser machining without pre-coloring^[37]; (e) inlet surface for laser machining with pre-coloring^[37]

Fig. 7. Millisecond laser processed holes on silicon nitride ceramics^[38]. (a) Effect of pulse duration on crack length；(b) effect of repetition rate on crack length

Fig. 8. Effects of processing environment on millisecond laser processed holes on aluminum oxide ceramics ^[23].(a)(b) In air; (c) under water

Fig. 9. Diameters and tapers of millisecond laser processed holes on aluminum oxide ceramics. (a) Effect of offset of focus spot of CO₂ laser on hole diameter and taper^[40]; (b) effect of auxiliary gas pressure on CO₂ laser processed hole diameter and taper^[40]; (c) effect of offset of focus spot of optical fiber laser on hole diameter and taper^[40]; (d) effect of auxiliary gas pressure on optical fiber laser processed hole diameter and taper^[40]; (e) effect of repetition rate on CO₂ laser processed hole diameter and taper^[41]; (f) effect of average power on optical fiber laser processed hole diameter and taper^[41]; (g) effect of pulse duration on hole taper^[41]

Fig. 10. Holes ablated by millisecond laser processing on silicon carbide ^[30]. (a) Effect of spot scanning speed on hole taper; (b) SEM images of hole sidewall

Fig. 11. Sidewall images of millisecond laser processed holes on aluminum oxide ceramics. (a) Under different energy densities^[41]; (b) under different numbers of pulses^[42-43]; (c) before optimization^[40]; (d) after optimization^[40]

Fig. 12. Sidewall images and surface morphologies of millisecond laser processed holes on aluminum oxide ceramics^[34]. (a) Side profiles of hole; (b) recast layer and crack of hole sidewall; (c) SEM image of hole sidewall; (d) recast layer of hole sidewall

Fig. 13. Millisecond laser or water-jet assisted laser processed holes on aluminum oxide ceramics. (a) Schematic of water-jet assisted laser processing^[32]; (b)(c) laser processed hole^[45]; (d)(e) water-jet assisted laser processed hole^[45]; (f) effect of water-jet velocity on thickness of recast layer^[45]

Fig. 14. Grains of aluminum oxide ceramics. (a) Heat affected zone ^[34]; (b) recast layer^[36]; (c) substrate^[21]; (d)(e) heat affected zone^[21]

Fig. 15. Nanosecond laser processed holes on silicon nitride ceramics^[55-56]. (a) Effect of repetition rate on hole circularity; (b) effect of scanning pitch on hole circularity

Fig. 16. Nanosecond laser processed holes on aluminum nitride ceramics. (a1)(a4)Inlets for ten scanning times；(b1)(b4)outlets for ten scanning times; (c1)(c4) inlets for fifty scanning times; (d1)(d4)outlets for fifty scanning times

Fig. 17. Nanosecond laser processed holes on aluminium oxide and aluminum nitride ceramics. (a) SEM image of aluminum nitride hole^[57]; (b) element content in heat affected zone of aluminum nitride hole^[57]; (c) element content in heat affected zone of aluminum oxide hole^[24]

Fig. 18. Inlets of nanosecond laser processed holes on aluminum oxide ceramics^[24]. (a) SEM image of hole；(b) partially enlarged hole; (c)(d) cracks of hole

Fig. 19. Nanosecond laser processed holes on aluminum oxide ceramics^[24]. (a) Average temperature of sample surface；(b) temperature at center of sample surface

Fig. 20. Nanosecond laser processed holes on silicon carbide and aluminum oxide ceramics. (a) Effect of scanning pitch on silicon carbide hole taper^[56]; (b)(c)(d) effect of trepanning pattern on aluminum oxide hole taper^[24,60]; (e) effect of scanning speed on aluminum oxide hole taper^[24,60]

Fig. 21. Nanosecond laser processed holes on silicon carbide ceramics. (a) Effect of laser fluence on hole taper under different solutions^[59]; (b) effect of air and water environment on hole taper^[61]

Fig. 22. Nanosecond laser processed holes on aluminum nitride ceramics^[62-63]. (a) Effect of jump direction on morphology of hole sidewall; (b) effect of scanning mode on morphology of hole sidewall

Fig. 23. Sidewall images of nanosecond laser processed holes on aluminum oxide ceramics^[64]. (a)(b) Recast layer；(c)(d) microcracks; (e)(f) microcracks spreading along grain boundaries

Fig. 24. Femtosecond laser processed holes on aluminum oxide ceramics. (a) Schematic of hole processing with fixed starting point and variable starting point^[72]; (b) hole processed with fixed starting point^[72]; (c) hole processed with variable starting point^[72]; (d) effect of interpolation error on hole circularity^[24]

Fig. 25. Holes ablated by femtosecond laser processing on aluminum oxide ceramics^[73]. (a) Hole morphology induced by gentle ablation; (b) hole morphology induced by strong ablation; (c) hole morphology induced by gentle ablation and strong ablation

Fig. 26. Femtosecond laser ablated holes on ceramics^[76]. (a) Aluminum oxide ceramics; (b) aluminium nitride ceramics

Fig. 27. Holes ablated with percussion and trepanning drilling by femtosecond laser processing on aluminum oxide ceramics^[78]. (a) Effect of laser fluence on spattering range of hole surface debris; (b) effect of scanning speed on spattering range of hole surface debris; (c) SEM image of percussion drilled hole; (d) SEM image of trepanning processed hole

Fig. 28. Inlet and outlet of femtosecond laser processed holes on aluminum oxide ceramics^[80]. (a) Single circle trepanning; (b) 3 circle partial filling trepanning; (c) multi-group interval machining; (d) SEM image of hole

Fig. 29. Control method of hole taper by femtosecond laser processing on ceramics. (a) Effect of focus position on femtosecond laser processed hole diameter and taper on aluminum oxide ceramics^[80]; (b) helical laser path^[81]

Fig. 30. Ultrafast laser processed holes on aluminum oxide ceramics. (a) Schematic of laser machining mechanism of hole^[82]; (b) schematic of semi-submerged assisted laser machining mechanism of hole^[82]; (c) holes ablated in air with different single pulse energies^[83-84]; (d) holes ablated under water with different single pulse energies^[83-84]; (e) holes ablated in air with different repetition rates^[85]; (f) holes ablated under water with different repetition rates^[85]

Fig. 31. Ultrafast laser processed holes on ceramics. (a) Effect of auxiliary gas pressure on hole taper^[71,86]; (b) effect of lens focal length on hole taper^[88]

Fig. 32. SEM images of ultrafast laser processed holes on aluminum oxide ceramics. (a)(b) Percussion drilled holes^[78]；(c)(d) trepanning processed holes^[78]; (e)(f) holes processed in air^[83-84]; (g)(h) holes processed under water^[83-84]