Polymers were one of the first materials to be processed by ultrafast lasers. However, the nature of absorption for near-infrared laser beams is not fully understood, and therefore it remains challenging to process polymeric materials with high energy efficiency. In this study, the pulse-to-pulse evolution of optical properties (reflectance, transmittance, and absorptance) of polypropylene (PP), which is an important polymeric material widely used in many industrial applications, is determined by performing time-resolved measurements for a wide range of pulse energies. The goal is to differentiate between linear and nonlinear absorption in different laser-matter interaction regimes and select the processing condition that yields the highest energy efficiency. The experiment is performed by recording the reflection and transmission of each laser pulse in an ellipsoidal mirror-based setup, which enables the collection of scattering reflection with nearly full coverage. Absorption is calculated from the experimental data, and a model consisting of linear and nonlinear absorption is used to analyze the results. It is found that PP undergoes a dramatic morphological change from pulse to pulse, which is accompanied by changes in optical properties, that is, the tuning of the laser condition to fully utilize the laser energy. Their results could help increase energy efficiency in ultrashort-pulsed laser processing of polymers toward the high-throughput operation.

中文翻译：

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聚合物超快激光微加工中光学性能的逐脉冲演变

聚合物是超快激光加工的首批材料之一。然而，对于近红外激光束的吸收性质还没有被完全理解，因此以高能量效率处理聚合物材料仍然具有挑战性。在这项研究中，聚丙烯（PP）是一种在许多工业应用中广泛使用的重要聚合材料，其光学特性（反射率，透射率和吸收率）在脉冲之间的演变是通过进行时间分辨测量来确定的。广泛的脉冲能量。目的是在不同的激光物质相互作用方式中区分线性吸收和非线性吸收，并选择产生最高能量效率的加工条件。通过在基于椭球镜的设置中记录每个激光脉冲的反射和透射来执行该实验，从而可以收集几乎全覆盖的散射反射。根据实验数据计算吸收，并使用由线性和非线性吸收组成的模型来分析结果。发现PP在脉冲之间经历急剧的形态变化，其伴随着光学性质的变化，即，调节激光条件以充分利用激光能量。他们的结果可能有助于提高聚合物的超短脉冲激光加工向高通量操作的能源效率。根据实验数据计算吸收，并使用由线性和非线性吸收组成的模型来分析结果。发现PP在脉冲之间经历急剧的形态变化，其伴随着光学性质的变化，即，调节激光条件以充分利用激光能量。他们的结果可能有助于提高聚合物的超短脉冲激光加工向高通量操作的能源效率。根据实验数据计算吸收，并使用由线性和非线性吸收组成的模型来分析结果。发现PP在脉冲之间经历急剧的形态变化，其伴随着光学性质的变化，即，调节激光条件以充分利用激光能量。他们的结果可能有助于提高聚合物的超短脉冲激光加工向高通量操作的能源效率。