飞秒激光多脉冲烧蚀过程中飞秒时间分辨电子状态的观测研究  

Femtosecond Time-Resolved Electronic States in Femtosecond Laser Multipulse Ablation

作　　者：王谦豪 赵华龙[1] 杨小君[1] 温文龙[1] 李益 Wang Qianhao;Zhao Hualong;Yang Xiaojun;Wen Wenlong;Li Yi(Photonic Manufacturing System and Application Research Center,Xi’an Institute of Optics and Precision Mechanics,Chinese Academy of Sciences,Xi’an 710119,Shaanxi,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院西安光学精密机械研究所光子制造系统与应用研究中心,陕西西安710119 [2]中国科学院大学,北京100049

出　　处：《中国激光》2023年第24期1-11,共11页Chinese Journal of Lasers

摘　　要：为研究飞秒激光加工硬脆透明材料时存在的“微裂纹”与“诱导条纹”等共性工艺问题,利用飞秒时间分辨泵浦探测阴影成像技术,对飞秒激光多脉冲烧蚀石英玻璃过程中的电子动力学过程进行成像,分析了激光脉冲电离材料初期(700 fs之前)等离子体丝的演化情况。多脉冲诱导微结构的存在使成丝区域分布在微结构的两侧与光脉冲传播的轴线方向,前者主要是由微结构侧壁对光脉冲的折射造成的,而后者则是由微结构底面与侧壁形貌不同导致的光程差引起的。实验结果揭示了多脉冲加工过程中脉冲串诱导微结构对后续光场的重塑效应,该效应影响了等离子体成丝区域与能量沉积的分布,这是共性工艺问题产生的核心机制。Objective This study investigates the prevalent process problems,such as “microcracking” and “induced streaking,” in the femtosecond laser processing of hard and brittle transparent materials.The study employs the femtosecond time-resolved pump-probe shadow imaging technique to visualize the electron dynamics during the femtosecond laser multi-pulse ablation of quartz glass.Particularly,the plasma filament evolution at the early stage of laser pulse ionization(before 700 fs) is analyzed.The multi-pulseinduced microstructures distribute the filament formation regions on both sides of the microstructure with respect to the axial direction of the light pulse propagation.The distribution on both sides is primarily due to the refraction of the light pulse by the sidewalls of the microstructure,while that on the axis is caused by the difference in the shape of the bottom and sidewalls of the microstructure,creating the light range difference.The empirical results show that the pulse train induces a remodeling effect of the microstructure on the subsequent light field during multi-pulse processing,affecting the distribution of the plasma filament formation region and energy deposition—the core mechanism responsible for common process problems.Methods A femtosecond time-resolved pump-probe shadow imaging setup was built to capture the propagation and ionization process of a single subsequent pulse beneath the microstructure induced by irradiating the material with 219 fs pulses.First,the actual spatial location of the focus was determined by imaging the shadow of the air-ionized plasma at the focus.After that,the power density at the material surface was obtained for different focus positions.The distinctive “V” and “inverted trapezoid” shapes were obtained after controlling the relative positions of the laser focus and the material.Second,the ionization process of femtosecond timeresolved propagation of the 220th pulse under different microstructures was obtained by modulating the time delay between pu

关 键 词：激光技术 飞秒激光微加工 泵浦探测阴影成像 多脉冲烧蚀 等离子体 

分 类 号：TN249[电子电信—物理电子学]