基于光学传感测量的飞秒激光烧蚀过程的动力学特性研究

发布时间：2018-03-07 16:06

本文选题：光纤传感　切入点：飞秒激光　出处：《武汉理工大学》2015年博士论文　论文类型：学位论文

【摘要】：由于飞秒激光与物质相互作用的多样性和复杂性,并且飞秒激光在微纳米加工、激光推进、冲击强化处理、生物医疗等领域具有重要的应用价值,因此,飞秒激光烧蚀机理成为飞秒激光应用领域的热点研究内容。本文针对飞秒激光烧蚀过程产生微等离子体及微等离子体冲击波进展的复杂性,提出运用光学传感测量技术从理论和实验两方面研究了飞秒激光烧蚀过程的动力学特性。探索了飞秒激光烧蚀过程中影响动力学特性的参量变化情况,包括电子密度、冲击压强等。设计了一种运用抽运探测技术探测飞秒激光烧蚀晶体材料产生微等离子体的膨胀过程的实验系统;建立了一种利用ICCD拍摄微等离子体动态过程的高速摄影实验系统;设计了一套基于全光纤无胶微结构探针型光纤F-P声发射传感器的在线监测系统;获得了一种利用光纤F-P声发射传感探针在线监测飞秒激光烧蚀晶体材料产生微等离子体冲击波的动力学过程的新原理、新技术;初步探索了一种晶体材料成分检测的新方法。主要研究工作如下:(1)针对飞秒激光烧蚀过程产生微等离子体的复杂性,运用抽运探测技术,建立了飞秒激光烧蚀晶体材料的时间分辨抽运探测系统。将不同飞秒激光能量、不同晶体材料的实验条件下产生微等离子体的动态过程用时间分辨阴影图进行描述和分析。研究了不同能量、不同晶体材料的微等离子体冲击波的法线方向、切线方向传播速度、传播距离等的变化规律,揭示了不同能量、不同晶体材料的微等离子体冲击波的冲击波速、冲击压强的变化规律。初步确定了影响飞秒激光微等离子体动力学过程的基本因素。(2)运用高速摄影法在不同激光能量下对飞秒激光烧蚀不同晶体材料产生微等离子体动态过程进行了研究。高速摄影法直观地显示了激光微等离子体的发展变化过程。研究发现飞秒激光烧蚀晶体材料产生微等离子体在空间上呈液滴状,微等离子体闪光的纵向尺寸比水平方向的尺寸大。随着飞秒激光能量的增大微等离子体在空间上的尺寸也随着增加,在纵向微等离子体的尺寸产生明显的变化趋势,而在水平方向的变化较为缓慢。这些结论对以后更深入地研究高强度飞秒激光应用以及飞秒激光与物质相互作用具有重要的指导意义。(3)根据F-P光纤传感原理和激光等离子体冲击波声学理论,设计与制作了能够监测相应频率的高灵敏度、全光纤无胶微结构探针型F-P声发射传感器,设计了用于飞秒激光微等离子体在线监测的光纤传感信号解调系统,设计了基于光纤传感技术的飞秒激光微等离子体冲击波的测量系统。实验结果表明,该传感测量系统可测量飞秒激光等离子体冲击波面微弱声发射高频信号。使不同飞秒激光脉冲内的微等离子体声发射信号的非接触式探测变成现实,减小了由于接触式探测信号以及重复测量带来的误差,保证了实验的准确性。(4)首次采用光纤F-P声发射探针在线监测飞秒激光微等离子体冲击波的时空进程,通过在线监测飞秒激光微等离子体冲击波的声学信号,分析飞秒激光微等离子体冲击波的时空历程,建立一种新型的激光微等离子体冲击波动力学过程监测的传感理论和方法。实验研究了光纤F-P声发射传感探针在线监测飞秒激光烧蚀过程所产生的微等离子体冲击波的时空变化规律及声发射信号的时频特性。研究发现:该飞秒激光烧蚀晶体材料产生的微等离子体声发射信号强度随激光能量的增大而增大;频率范围在0~100KHz;频率范围和峰值位置基本不随作用激光能量的改变而改变。不同晶体材料的频率峰值有细微的差异,同一晶体材料的频率峰值保持不变。(5)初步探索了一种晶体材料成分检测的新方法。提出了一种新颖的基于时频分析的飞秒激光微等离子体冲击波声发射信号的处理和分析方法,研究了飞秒激光微等离子体冲击波声发射信号的频率特征及能量分布;通过对探测到的信号的特征分析,初步实现了对晶体材料成分的检测。
[Abstract]:Due to the interaction of femtosecond laser and material diversity and complexity, and femtosecond laser micro machining, laser propulsion, laser shock processing, has important application value, medical and other fields. Therefore, femtosecond laser ablation mechanism has become a hot research field. The application of femtosecond laser based on femtosecond laser ablation process and micro plasma the complexity of micro plasma shock wave in the proposed dynamic characteristics of femtosecond laser ablation process is studied from two aspects of theory and experiment using optical sensing technology. To explore the changes of parameters influencing the dynamic characteristics of femtosecond laser ablation process, including electron density, impact pressure. Design a pump probe using the expansion process the detection technology of femtosecond laser ablation of crystal materials to produce micro plasma experimental system; establish a by ICCD Experimental system for high-speed photography shooting micro plasma dynamic process; a set of online monitoring system of all fiber without glue micro structure probe type optical fiber F-P acoustic emission sensor is designed based on the new technology; obtain a F-P acoustic emission sensor using optical fiber probe monitoring of femtosecond laser ablation of crystal materials to produce new principle, micro plasma shock wave dynamics the preliminary exploration; a new method of crystal material composition detection. The main research work is as follows: (1) the complexity of micro plasma generation in femtosecond laser ablation process, using the pump probe technique, a femtosecond laser ablation of crystal materials time-resolved pump probe system. Different femtosecond laser energy, dynamic the process of producing micro plasma crystal materials under different experimental conditions with time resolution are described and analyzed. The shadow map of different energy, not Micro plasma shock wave normal direction with crystal materials, the tangent velocity, variation propagation distance, reveals the different energy shock wave, micro plasma wave velocity of different crystal materials, changes of impact pressure. Initially determined the basic influence factors of femtosecond laser micro plasma process. (2 the use of high speed photography) under different laser energy of femtosecond laser ablation of different crystal materials to produce micro plasma dynamic process was studied. High speed photography can visually display the change and development of laser micro plasma process. The study found that femtosecond laser ablation of crystal material to produce micro plasma liquid in the space, the longitudinal dimension of micro plasma flash the ratio of horizontal size. With the increasing of the size of the femtosecond laser micro plasma energy in the space with the increase Plus, have obvious trend in the longitudinal micro plasma size, and changes in the horizontal direction is relatively slow. These conclusions for the future more in-depth study on the interaction of high intensity femtosecond laser and femtosecond laser and matter has an important guiding significance. (3) according to the wave theory of F-P fiber acoustic sensing principle and laser plasma shock and the design and manufacture of high sensitivity to monitoring the corresponding frequency, all fiber Non Gel micro structure probe type F-P acoustic emission sensor, optical fiber sensing signal demodulation system for on-line monitoring of femtosecond laser micro plasma is designed. The design of optical fiber sensing technology of femtosecond laser micro plasma shock wave measurement system. Based on the experimental results show that the sensing system can wave weak acoustic measurement of femtosecond laser plasma shock emission of high frequency signals. The femtosecond laser pulse in micro Non contact type plasma acoustic emission signal detection into reality, reduce the error due to contact detection signal and repeat measurement, to ensure the accuracy of the experiment. (4) for the first time using optical fiber F-P acoustic emission monitoring probe femtosecond laser plasma shock wave spatio-temporal process, through the on-line monitoring of femtosecond laser plasma shock acoustic signal wave analysis, femtosecond laser plasma shock wave of the course of history, the establishment of a new micro laser plasma shock wave dynamics sensing theory and method of process monitoring. Experimental study on micro plasma shock time spacedistributions and AE signal time-frequency characteristics of wave generated by the sensing probe for on-line monitoring of femtosecond laser ablation process of F-P fiber AE. Studies have found that the femtosecond laser ablation of crystal micro plasma acoustic emission signal The degree of increase with laser energy increasing; in the frequency range 0~100KHz; frequency range and peak position approximately with the laser energy change. The peak frequency of different crystal materials have subtle differences, with a peak frequency of crystal materials remain unchanged. (5) explored a new method of crystal materials detection. This paper presents a novel time-frequency analysis based on the femtosecond laser plasma shock wave processing and analysis method of AE signal, the femtosecond laser plasma shock wave frequency characteristics and energy distribution of acoustic emission signals; signal through the analysis of detected, realized the detection of crystal materials component.

【学位授予单位】：武汉理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN249

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