基于飞秒激光微加工的光纤传感器制备及其传感特性研究

发布时间：2018-06-23 08:31

本文选题：飞秒激光 + 微加工　；参考：《浙江大学》2016年博士论文

【摘要】：光纤传感系统具有灵敏度高、结构精巧、抗电磁干扰、耐腐蚀并能实现分布式测量等优势,在科研、生产、安全等领域的应用日益增加。飞秒激光具有超短的脉冲宽度、超高的峰值功率,从根本上改变了激光加工过程中的光与材料的作用机理,具有精度高、加工材料广泛及真三维加工等优势,被广泛应用于各种功能器件的加工过程。本论文以飞秒激光加工的光纤微结构传感器为中心内容,从传感机理、模式分析、数值仿真、制作工艺及传感测试等方面展开研究,并对加工光束的优化问题进行了探讨。论文的主要创新性工作包括以下三个方面：(1)开展了基于微拉锥的光纤内微腔传感技术研究,获得了一种多功能、小体积、高强度、低成本的光纤传感器。理论分析了基于内置微腔的干涉型光纤传感器机理,对双光束干涉公式解析得到传感器的温度、纵向应力及外界折射率传感灵敏度均与模式阶数有关的结论;建模并仿真分析了微腔壁中的传导模式,探讨了传感器在纵向应力及折射率传感时存在红移或蓝移的可能性；实验研究了光纤内置微腔传感器的制作方法,确定了飞秒激光烧蚀-熔接-微拉锥的三步法制作流程并优化了工艺参数;测试了微拉锥内微腔干涉仪在温度、应力和折射率方面的传感性能,实验获得了与理论研究一致的结果;实现了微拉锥内微腔干涉仪用于温度与应力同时测量;为增强器件对外部折射率的响应进行了微腔壁的减薄处理,实验获得该器件在低折射率区间灵敏度达到4202nm/RIU,较微拉锥微腔传感器提升约100倍。(2)开展了基于选择填充光子晶体光纤的传感技术研究,获得了一种设计灵活、制备可控的弯曲矢量传感器。理论研究了选择填充光子晶体光纤耦合器的传感机理,建模并仿真分析了光子晶体光纤结构参数及填充材料对耦合器传感性能的影响;以正交位置填充不同折射率液的方案,设计了能够实现全空间弯曲矢量测量的传感器;实验研究了以飞秒激光为关键加工手段的选择填充光子晶体光纤耦合器的制备方法;测试了耦合器的弯曲传感特性,在0-10.7m-1曲率范围内获得具方向指示的线性响应,灵敏度达到-1.20nm/m-1,实验结果与理论分析高度统一,为特殊功能传感器的设计和制备提供了可靠的依据。(3)开展了飞秒激光加工光束的优化技术研究,设计了一种能够减小光斑横向尺寸并延长焦深的光瞳滤波器。以矢量衍射方法计算了径向偏振光在聚焦点附近的光强分布;分析了影响光斑尺寸的主要因素并以此为依据设计了连续相位型光瞳滤波器;以横向超分辨因子为优化目标,施特列尔比为约束条件对滤波函数进行了优化,计算结果表明在保持较高能量利用率的同时(S=0.5),获得了更小的聚焦光斑(GT=0.75)。
[Abstract]:The optical fiber sensing system has many advantages such as high sensitivity, fine structure, anti-electromagnetic interference, corrosion resistance and distributed measurement. It is widely used in scientific research, production, safety and other fields. Femtosecond laser has ultrashort pulse width and super-high peak power, which fundamentally changes the action mechanism of light and material during laser processing, and has the advantages of high precision, wide range of machining materials and true three-dimensional machining. It is widely used in the machining process of various functional devices. In this paper, the optical fiber micro-structure sensor fabricated by femtosecond laser is the focus of this paper. The research is carried out from the aspects of sensing mechanism, mode analysis, numerical simulation, fabrication technology and sensing test, and the optimization of the processing beam is discussed. The main innovative work includes the following three aspects: (1) A multi-functional, small volume, high strength and low cost optical fiber sensor is obtained by researching the micro-cavity sensing technology based on micro-tapered fiber. The mechanism of interferometric optical fiber sensor based on built-in microcavity is analyzed theoretically. The conclusion that the temperature, longitudinal stress and sensitivity of external refractive index sensor are related to the order of mode is obtained by analyzing the two-beam interferometric formula. The conduction mode in the microcavity wall is modeled and simulated, and the possibility of redshift or blue shift in the longitudinal stress and refractive index sensor is discussed, and the fabrication method of the fiber optic microcavity sensor is studied experimentally. The three-step fabrication process of femtosecond laser ablation, welding and microtaper was determined, and the process parameters were optimized, and the sensing performance of the micro-cavity interferometer in the micro-pulling cone was tested in terms of temperature, stress and refractive index. The experimental results are in agreement with the theoretical study. The microcavity interferometer is used to measure temperature and stress simultaneously. In order to enhance the response of the device to the external refractive index, the microcavity wall is thinned. Experimental results show that the sensitivity of the device in the low refractive index range is 420nm / r IUs, which is about 100 times higher than that of the micro-cavity sensor. (2) the sensor technology based on optionally filled photonic crystal fiber is studied, and a flexible design is obtained. A controllable bending vector sensor is fabricated. The sensing mechanism of optionally filled photonic crystal fiber coupler is studied theoretically, and the influence of the structure parameters of photonic crystal fiber and the filling material on the sensing performance of the coupler is simulated and analyzed. The sensor which can realize the full space bending vector measurement is designed, the fabrication method of the optionally filled photonic crystal fiber coupler with femtosecond laser as the key processing method is studied experimentally, and the bending sensing characteristics of the coupler are tested. The linear response with direction indication is obtained in the range of 0-10.7m-1 curvature. The sensitivity is -1.20 nm / m ~ (-1). The experimental results are in good agreement with the theoretical analysis. It provides a reliable basis for the design and fabrication of special functional sensors. (3) the optimization technology of femtosecond laser processing beam is studied and a pupil filter is designed which can reduce the transverse size of the spot and prolong the focal depth. The intensity distribution of radial polarized light near the focal point is calculated by using vector diffraction method. The main factors affecting the size of the spot are analyzed and the continuous phase pupil filter is designed based on it. The transverse super resolution factor is used as the optimization target. The filter function is optimized by using Stellsby as a constraint condition. The calculation results show that a smaller focused spot (GTN 0.75) can be obtained while maintaining a higher energy utilization ratio (S0. 5).
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP212

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