Quality and throughput of laser material processing are influenced by multiple laser parameters as well as material properties. Since material degradation due to laser processing is generally related to heat-affected zone, quick optimization and realization of nonthermal process is one of the most important issues for higher-grade laser processing. In this work, we developed various parameter-controlled ultrashort pulse laser system that can control various laser parameters over a wide range, such as pulse duration over three orders of magnitude. Using this laser system (wavelength: 1033 nm, pulse duration: 0.4 to 400 ps, repetition: up to 1 MHz), we have investigated nonthermal–thermal processing boundary in drilling of ceramics: aluminum nitride (AlN) and yttria-stabilized zirconia (YSZ), with high and low thermal conductivity, respectively. As a result, the AlN ceramic exhibited strong dependence of ablation rate on fluence: low-, mid- and high-fluence regimes appeared with different logarithmic correlations. Further, the nonthermal–thermal process boundaries appeared, depending on the pulse duration. On the other hand, the ablation behavior of YSZ was much different from AlN; the ablation rate did not show distinct three regimes. Further, there were no nonthermal process windows for the YSZ. Therefore, the nonthermal–thermal process boundaries were governed by the laser parameters like pulse duration as well as the material thermal conductivity.

中文翻译：

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大范围变参数超短脉冲激光系统陶瓷钻孔非热加工边界研究

激光材料加工的质量和产量受多种激光参数和材料特性的影响。由于激光加工引起的材料退化通常与热影响区有关，因此快速优化和实现非热加工是更高级的激光加工最重要的问题之一。在这项工作中，我们开发了各种参数控制的超短脉冲激光系统，可以在很宽的范围内控制各种激光参数，例如超过三个数量级的脉冲持续时间。使用该激光系统（波长：1033 nm，脉冲持续时间：0.4 至 400 ps，重复频率：高达 1 MHz），我们研究了陶瓷钻孔中的非热处理-热处理边界：氮化铝 (AlN) 和氧化钇稳定的氧化锆（ YSZ)，分别具有高和低热导率。结果，AlN 陶瓷表现出烧蚀速率对注量的强烈依赖性：低、中和高注量区域出现具有不同的对数相关性。此外，出现了非热-热过程边界，这取决于脉冲持续时间。另一方面，YSZ 的烧蚀行为与 AlN 有很大不同；消融率没有显示出明显的三种制度。此外，YSZ 没有非热处理窗口。因此，非热-热过程边界受激光参数控制，如脉冲持续时间和材料热导率。取决于脉冲持续时间。另一方面，YSZ 的烧蚀行为与 AlN 有很大不同；消融率没有显示出明显的三种制度。此外，YSZ 没有非热处理窗口。因此，非热-热过程边界受激光参数控制，如脉冲持续时间和材料热导率。取决于脉冲持续时间。另一方面，YSZ 的烧蚀行为与 AlN 有很大不同；消融率没有显示出明显的三种制度。此外，YSZ 没有非热处理窗口。因此，非热-热过程边界受激光参数控制，如脉冲持续时间和材料热导率。