A nanosecond-millisecond combined pulse laser (CPL) drilling method was proposed for drilling alumina ceramic. The total energy consumption of the CPL drilling was 1/7 of that of a conventional millisecond laser, and the drilling quality was better. The simulation results demonstrated that, due to the nonuniform reflection of the millisecond laser in the keyhole, the ellipse keyhole ablated by the off-axis incident nanosecond pulses had no effect on the circularity of the through hole. In addition, the multireflection of the laser in the keyhole enhanced the absorption, so the keyhole ablated by the nanosecond pulses could be used as a target for limiting the absorption of the subsequent millisecond pulses. In this context, the keyhole could be used to reduce the hole diameter if the subsequent millisecond laser had a bigger spot size, and this CPL drilling method could be used as an effective group hole drilling method.

中文翻译：

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氧化铝陶瓷的纳秒-毫秒组合脉冲激光钻孔

提出了一种纳秒-毫秒联合脉冲激光（CPL）钻孔方法，用于氧化铝陶瓷的钻孔。CPL钻孔的总能耗是传统毫秒激光的总能耗的1/7，钻孔质量更好。仿真结果表明，由于毫秒激光在匙孔中的反射不均匀，离轴入射纳秒脉冲烧蚀的椭圆形匙孔对通孔的圆度没有影响。另外，激光在小孔中的多次反射增强了吸收，因此被纳秒脉冲消融的小孔可用作限制后续毫秒脉冲吸收的目标。在这种情况下，如果随后的毫秒激光具有较大的光斑尺寸，则可以使用锁孔减小孔径。