| 题名 | 短脉冲激光烧蚀理论及楔条形阳极加工方法研究 |
| 作者 | 金方圆 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院大学 |
| 导师 | 陈波 |
| 关键词 | 激光加工 短脉冲激光 双温模型 有限元方法 楔条形阳极 |
| 其他题名 | Ultrashort laser ablation: fundamental and its application in fabricating wedge and strip anode |
| 学位专业 | 光学工程 |
| 中文摘要 | 短脉冲激光有着脉冲宽度较窄、能量密度高、加工效率高、热影响区小的特点，在微纳加工、微电子学、测量系统、医学和航天科技等领域得到广泛的应用。但是，短脉冲激光微加工技术的原理还未被完全认知。本文深入研究了短脉冲激光烧蚀理论，并研究了楔条形阳极的加工检测方法，为提高楔条形阳极光子计数成像探测器性能提供了理论和实验依据。具体的研究内容和研究方法为： 1、利用加权余量的迦辽金方法导出了双温热传导微分方程组的等效积分公式；使用格林公式，推导出双温热传导方程组的等效积分的“弱形式”；采用直接积分的方法，得到求解双温有限元模型所需时间步长、网格密度等参数；根据短脉冲激光去除材料的基本理论，分析了飞秒激光烧蚀铝膜的相变区域。 2、将Drude理论加入到双温模型中，准确地描述了激光烧蚀材料过程中表面的反射率系数和热吸收系数的变化；利用相变过程中材料内部焓的变化，优化了双温模型；研究了低能量密度皮秒激光辐照铝膜的热弹性力学模型；分析了铝膜内部的形变及热应力的变化，验证了热弹性波的存在及电子的热爆发力对弹性波的推进作用。 3、为研究铝膜受短脉冲激光作用的能量传输过程，建立了一维半经典双温热传导有限元模型，得到晶格温度随时间分布的规律；根据自由电子气理论优化了模型，得到铝膜表面反射率和热吸收系数随时间分布图；描绘了激光辐照所产生热电场和电子漂移运动速度分布规律，证明激光作用产生的热电场是电子漂移运动的主导因素；定义了过热加热区，得到激光烧蚀深度随时间变化关系，单脉冲激光烧蚀深度与实验相符。 4、对石英衬底上微米量级厚度的铝膜进行了烧蚀，研究了光斑重叠率对烧蚀图形以及重复加工次数对加工精度的影响；为提高加工精度和验证所求烧蚀率的准确性，提出重复多次加工的方法；对比了高斯线性法与高斯线性修正法的求解烧蚀率的结果，证明了高斯线性修正法在扫描激光精细加工方面的优越性。利用高斯线性修正法求得的烧蚀效率，模拟了激光在不同光斑重叠率下烧蚀微槽的三维轮廓图。 5、通过对激光旋转参数以及平台移动参数的理论分析，得到加工楔条形阳极绝缘沟槽所需参数；使用离焦加工的方法，加工出高质量的楔条形位敏阳极，进行了电荷直接收集法和感应电荷读出方式成像实验；使用有限元计算的方法得到阳极的每个导电电极的感应电荷量，计算了直径为65 mm的楔条形阳极的在电荷云半径为4 mm下的位置解码公式和边缘非线性效应。 |
| 英文摘要 | Ultrashort, sub-picosecond lasers bring new opportunities in a variety of technological applications in miro- to nanotechnologies, micro-electronics, measurement and microscopy, medicine industry, biotechnology and aerospace industry. However, the processes governing ultrashort pulsed laser ablation are not completely understood at the moment. In order to fabricate Wedge and Strip Anode (WSA) with high quality, the basic theory of ultrashort laser processing material is analyzed, and the fabrication and testing method of WSA is studied. Regarding on these questions, the main contents, methods and achievements are presented as follows: 1. The Galerkin Weighted Residual Method is applied to induce the equivalent integral form of two temperature model (TTM), and the weak forms of TTM are deduced by Green formula, thus the finite element functions of TTM are obtained; The finite element functions of TTM are soluted to study the phase change region during femtosecond laser processing Al film. 2. The Drude model and free gas theory are proposed in this work to describe temperature-dependent optical reflectivity and absorption coefficient for laser ablating metal and dielectric materials, and the ultrafast phase change function is incorporated into the TTM to describe the solid to liquid phase change process; An ultrafast thermoelasticity based on TTM is used to study investigate the thermomechanical response of Al film irradiated by picosecond laser by using finite element method (FEM); The electron and lattice temperatures, displacements and stresses are depicted; Results show that the hot-electron blast force can boost the thermoelastic wave induced by picosecond laser. 3. A semi-classical two temperature model is studied with finite element calculation method; The spatial and temporal lattice temperature distribution map of Al film irradiated by 0.12 W picosecond laser is depicted; The phase explosion is found to be the reason for ablation; The over-heated zone (OHZ) is defined, and the calculated ablation depths of single pulses coincide with experiment for 10 picosecond lasers. 4. The relationship between ablation rate and single pulse laser fluence is studied and the effect of spot overlapping rates on profilograms of grooves is analyzed; The ablation rates calculated from Gaussian Linear method (Gl) are compared with Corrected Gaussian Linear method (CGL), experimental results show that CGL is suitable for calculating ablation rates of grooves; The 3D profilogram of grooves in Al film ablated by 10 ps at different spot overlapping rates are simulated through CGL calculated ablation rates. 5. The parameters for picosecond laser ablating insulated grooves of wedge and strip anode (WSA) are studied by theoretical and experimental analysis; Using defocused laser, the WSA is fabricated with high ablation precision and quality; The performances of wedge and strip anode detector with direct collection readout and induction readout methods are studied; The induce charge on every single electrode of WSA is calculated with finite element method; When the radius of charge cloud is 4 mm, the decoding equations and the marginal non-linear performance of fabricated WSA are ascertained. |
| 公开日期 | 2015-12-24 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ciomp.ac.cn/handle/181722/48853]  |
| 专题 | 长春光学精密机械与物理研究所_中科院长春光机所知识产出 |
| 推荐引用方式 GB/T 7714 | 金方圆. 短脉冲激光烧蚀理论及楔条形阳极加工方法研究[D]. 中国科学院大学. 2015. |
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