Water-assisted femtosecond laser drilling of alumina ceramics

In this study, we used a water-assisted femtosecond laser drilling method to drill holes in alumina ceramics. The morphology, diameter, taper angle, cross-section area, and sidewall characteristics of the holes were investigated, and the hole characteristics obtained in the presence of air were compared with those obtained under water assistance. Finally, the mechanism underlying the water-assisted femtosecond laser drilling of alumina ceramics was investigated. The results revealed that the drilling efficiency and quality of the holes improved significantly by using the water-assisted femtosecond laser drilling method, and the effect was considerably obvious at lower pulse repetition rates. At the pulse repetition rate of 25 kHz, the taper angle decreased by 64.19% to 4.20° and the hole cross-section area increased by 46% under water assistance. In addition, water assistance could reduce the amount of the residual debris and redeposition of ablated material on the hole sidewalls, and there were almost no residual debris and redeposition of ablated material on the hole sidewalls near the hole exit. Compared to the case when the drilling was carried out in the presence of air, the composition of the hole sidewalls changed slightly when the drilling was carried out in the presence of water. With an increase in the pulse repetition rate, more plasma was formed and the plasma shielding effect strengthened, which weakened the effect of water assistance. Therefore, in order to obtain high drilling efficiency and quality during the water-assisted femtosecond laser drilling of alumina ceramics, it is necessary to use a low pulse repetition rate. The results of this study will find potential application in the field of ceramic manufacturing.