Anisotropy of material removal during laser-induced plasma assisted ablation of sapphire

Sapphire crystals have a special lattice structure, which causes anisotropy in their processing quality due to anisotropy of the physical and mechanical properties. Laser-induced plasma assisted ablation (LIPAA) is a new processing technology used to process transparent, hard, and brittle materials. LIPAA is regarded as a photoelectric composite processing method that makes the material removal and surface generation mechanisms more complicated. In this study, a surface generated by LIPAA processing showed much higher quality than a surface generated by direct laser ablation. Moreover, LIPAA has the advantage of a lower etching energy threshold than that of infrared laser direct ablation. Infrared laser-induced plasma assisted ablation was performed on different sapphire crystal orientations to explore the influence of anisotropy on LIPAA processing. The LIPAA material removal rates for different sapphire planes were presented and compared with results for direct laser ablation focused ion beam (FIB) processing. The results showed that thermal removal was most dominant during LIPAA processing of sapphire. The material removal rate was highest in the [10 1 0] direction and lowest in the [112 0] direction.