Material processing by ultrafast lasers is an attractive technology for high-precision fabrication, such as cutting, drilling, and surface modification, of a wide range of material, including dielectrics, semiconductor, metals, and polymer composites. However, it is still challenging to apply ultrafast laser processing in many applications because some key processes, such as absorption and heat accumulation, are not fully understood, especially for polymeric materials, which have a low melting temperature and, therefore, are more vulnerable to thermal damage. In this study, an analytical solution to a transient, two-dimensional thermal model is derived using Duhamel's theorem and Hankel’s transform method to understand the effect of laser parameters during ultrafast laser interactions with polypropylene (PP), which is a material widely used in many industrial applications. To correlate with theoretical calculation, laser cutting experiments are carried out on PP sheets. This study found that the total energy absorbed in the material and the laser intensity are two important factors to estimate the laser processing performance. In addition, time-resolved measurements are performed by using fast photodiodes and an oscilloscope to understand the dynamics of ultrafast laser interactions during the laser cutting process. Transmitted and reflected signals are monitored and analyzed to extract information on nonlinearity and the absorption coefficient.

中文翻译：

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聚合物材料超快激光微切割过程中的吸收和温度分布

超快激光材料加工是一种极具吸引力的技术，可用于多种材料（包括电介质、半导体、金属和聚合物复合材料）的高精度制造，例如切割、钻孔和表面改性。然而，在许多应用中应用超快激光加工仍然具有挑战性，因为一些关键过程，如吸收和热量积累，尚未完全了解，特别是对于熔点较低的聚合物材料，因此更容易受到影响。热损伤。在这项研究中，使用 Duhamel 定理和 Hankel 变换方法推导出瞬态二维热模型的解析解，以了解激光参数在超快激光与聚丙烯 (PP) 相互作用过程中的影响，这是一种广泛用于许多工业应用的材料。为了与理论计算相关联，在 PP 片材上进行了激光切割实验。本研究发现，材料吸收的总能量和激光强度是评估激光加工性能的两个重要因素。此外，通过使用快速光电二极管和示波器进行时间分辨测量，以了解激光切割过程中超快激光相互作用的动态。对传输和反射信号进行监测和分析，以提取有关非线性和吸收系数的信息。本研究发现，材料吸收的总能量和激光强度是评估激光加工性能的两个重要因素。此外，通过使用快速光电二极管和示波器进行时间分辨测量，以了解激光切割过程中超快激光相互作用的动态。对传输和反射信号进行监测和分析，以提取有关非线性和吸收系数的信息。本研究发现，材料吸收的总能量和激光强度是评估激光加工性能的两个重要因素。此外，通过使用快速光电二极管和示波器进行时间分辨测量，以了解激光切割过程中超快激光相互作用的动态。对传输和反射信号进行监测和分析，以提取有关非线性和吸收系数的信息。