【作者】 王英；

【导师】 陆培祥；

【作者基本信息】 华中科技大学 ， 物理电子学， 2010， 博士

【摘要】 飞秒激光微加工由于加工精度高、质量好以及可实现三维加工等优点,被广泛应用于对各种材料的加工处理。由于脉冲时间极短(<1ps),在飞秒激光作用下,脉冲能量能够在极短的时间内注入焦点区域的材料内,有效抑制了加工过程中热效应的影响。利用飞秒激光微加工的这些独特优点,可以在多种材料表面或内部制作新颖的微型光器件。本论文开展了飞秒激光微加工硅晶片、石英玻璃及光纤材料的实验研究。结合理论分析与数值模拟,基于飞秒激光三维加工在石英玻璃内部制作了体光栅；利用飞秒激光烧蚀在光纤内部制作了几种新型光纤传感器件并实验研究了它们的传感特性。全文的主要研究内容如下：(1)以飞秒激光微加工硅晶片为例详细介绍了飞秒激光材料微加工的方法和过程,结合光学显微镜、扫描电子显微镜(SEM)及电子能谱仪(EDX)等技术与仪器,分析了飞秒激光对硅晶片进行钻孔与切割的形貌特征、烧蚀速率以及表面氧化特性,并采用优化的加工参数制备了应用于微机电系统(MEMS)的微型硅模具。(2)实验研究了飞秒激光对石英玻璃的烧蚀阈值及体内光学损伤阈值,以及飞秒激光在石英玻璃内部直写体光栅的加工工艺,并结合有限元方法(FEM)的模拟结果分析了体光栅的衍射特性。(3)开展了基于飞秒激光微细加工方法在单模光纤(SMF-28)上制备微孔折射率传感器件的实验研究,结合一个几何光学模型以及时域有限差分方法(FDTD)数值模拟,详细阐释了微孔折射率传感器的透射谱特性与工作原理。(4)基于飞秒激光钻孔方法,在单模光纤以及光子晶体光纤(LMA-10)上制备了微孔结构的长周期光纤光栅(LPFG),并结合有限元方法(FEM)模拟与局部耦合模理论计算分析了此类微孔结构长周期光纤光栅的透射谱特性；使用可调谐激光器及红外CCD观测了微孔结构长周期光纤光栅的模场形貌,并利用PDL测试仪分析了微孔结构长周期光纤光栅的偏振相关损耗(PDL)；通过填充标准折射率匹配液(Cargille),研究了单模光纤上的微孔结构长周期光纤光栅对折射率的灵敏度。(5)基于飞秒激光烧蚀,在单根单模光纤上制备了微米尺度的Mach-Zehnder干涉仪,根据双光束干涉公式分析了此类干涉仪的透射谱特性及其对折射率与温度的灵敏度,并实验研究了此类干涉仪对折射率以及温度的响应,证明这是一种具有极高灵敏度的折射率传感器件以及较高灵敏度的高温传感器件。更多还原

【Abstract】 Femtosecond laser micromachining has been widely used in materials processing for its high precision, good quality and capability of three-dimensional micromachining. The heat effect can be ignored during femtosecond laser micromachining since pulse energies can be deposited into materials in the vicinity of the focal volume in an ultrashort time scale due to the short pulse duration (<1 ps). Novel micro-optic devices and features can be fabricated at the surface or in the bulk of materials with the advantages aforementioned. In this dissertation, experimental study on the micromachining of silicon wafer, fused silica and fiber materials have been perfomed by use of the femtosecond laser micromachining methods. Combined with theoretical analysis and numerical simulation, volume gratings have been fabricated in the bulk of fused silica with femtosecond laser three-dimensional fabrication technique, and novel fiber sensors have been fabricated in fibers by direct femtosecond laser ablation and the corresponding sensitivities for sensing applications have been investigated experimentally. The main contents are listed as follows:(1) The materials micromachining methods and procedures with femtosecond laser micromachining have been investigated systematically, in the case of silicon wafer processing. The morphologies, surface oxidation in the vicinity of the ablated holes and cutting kerfs in silicon wafer have been studied with the help of optical microscopy, scanning electronic microscopy (SEM) and energy dispersive X-ray analysis (EDX), and a micro-mould has been fabricated with optimal processing parameters for applications in MEMS.(2) The ablation threshold and bulk damage threshold of fused silica have been investigated experimentally. The processing parameters on the fabrication of volume gratings have been studies and optimized, and the diffraction power spectra of the gratings have been conclusively characterized by experiments and numerical simulations.(3) Refractive index sensor based on a microhole in the conventional single mode fiber (SMF-28) has been fabricated by use of femtosecond laser micromachining. The transmission characteristics and working principal of the sensor are discussed with a simple geometrical optical model and numerical simulations.(4) Long-period fiber gratings (LPFG) have been fabricated by direct femtosecond laser drilling in single mode fiber (SMF-28, from Corning) and photonic crystal fibers (LMA-10, from NKT Photonics and all-solid photonic bandgap fiber, from YOFC). The resonance wavelength shift and transmission spectrum of the microhole-structured LPFG are analyzed with coupled-local mode theory and simulation results obtained by the finite element method (FEM). And the mode profiles in the near field of the microhole structured LPFG are measured with a tunable laser and an infrared CCD camera. Furthermore, the polarization denpendent loss (PDL) of the device has been tested with an all optical parameter analyzer, and the sensitivity to surrounding refractive index of the LPFG has also been investigated by use of standard RI liquids (from Cargille Laboratory).(5) Miniaturized fiber inline Mach-Zehnder interferometer has been fabricated in single mode fiber with femtosecond laser ablation, and its corresponding transmission characteristics and sensitivity to surrounding refractive index and temperature have been discussed with the well-known two-beam interference equation. Results show that the miniaturized fiber inline Mach-Zehnder interferometer is suitable for refractive index sensing and high-temperature sensing with high sensitivity.更多还原