【作者】 关寿华；

【导师】 于清旭；

【作者基本信息】 大连理工大学 ， 光学工程， 2015， 博士

【摘要】 光子晶体光纤(Photonic crystal fiber, PCF)具有特殊的气孔结构和导光机制,因此在光纤传感和通信领域具有巨大应用前景。本文针对PCF特性及其传感应用,对PCF中的模式及其特性、PCF长周期光栅(Long-period grating, PCF-LPG)和PCF马赫-曾德尔干涉仪(Mach-Zehnder interferometer, MZI, PCF-MZI)的特性及传感应用做了全面研究,主要内容包括以下几个方面：1.基于矢量有效折射率法研究了改变结构参数调节PCF色散的方法,发现零色散波长随占空比和比例系数变化分别有极大值和极小值的双极值特性。色散调节方法和极值特性可用于指导设计有特定色散的PCF。在800 nm附近飞秒激光器工作波长处,设计了分别具有约60 nm带宽的反常平坦色散、正常平坦色散和近零平坦色散的3种PCF。2.通过数值模拟研究了根据结构参数选择合适光栅周期指导制备PCF-LPG的方法,及优选结构参数等增强内折射率(nin)敏感特性的方法。对反共振反射型光波导PCF-LPG内折射率特性进行了研究,结果表明在高介质折射率传感领域灵敏度达到10-7 RIU/pm量级。提出并分析了PCF-LPG折射率双通道测量法：被测介质在光栅外和气孔内共同作用包层模,从而增强折射率敏感特性,制成高度灵敏的PCF-LPG折射率传感器。3.以HE11cl模为例研究PCF中包层模及其色散特性、nin特性与包层半径关系。发现半径、波长及nin变化时,环状模、HE11cl模和HE12cl模间会衍变；半径减小时,多个类似模式按相似规律变化。不同半径下同一模式的色散特性和nin特性不同；模次升高时,色散特性和nin特性整体变化和增强。发现适当减小半径可增强PCF-LPG内折射率特性。4.理论与实验研究了多种因素对PCF-MZI应变特性的影响；制作了光纤环镜反射型PCF-MZI,测试表明具有较大条纹可见度和较窄带宽,能提高分辨率,应变灵敏度为-2.53 pm/με。设计制作了具有流线型熔接区的大线径PCF-MZI,测试表明应变灵敏度为-1.77 pm/με,折射率特性很弱,此种MZI适用于折射率特性不敏感的应变传感领域。5.设计并制备了阶梯式横向大偏置结构光纤MZI折射率传感器,研究了干涉原理、谱特性和折射率敏感特性。实验结果表明此种MZI灵敏度较高,长327μm和436μm的PCF-MZI和普通单模光纤MZI的灵敏度分别为2.17*10-7 RIU/pm和3.12*10-8 RIU/pm,灵敏度随着MZI长度减小而提高。制备了横向大偏置结构PCF-MZI,理论分析了干涉原理和折射率传感机制,折射率特性测试表明长330 μmPCF-MZI的灵敏度达到6.62* 10-8 RIU/pm。两种光纤MZI适于制成高度灵敏、快速测量的折射率传感器。更多还原

【Abstract】 Photonic crystal fiber (PCF) has great application prospect in the field of fiber sensing and communication, due to the special air-hole structure and light guiding mechanism. Being aimed at the characteristics and sensing applications of PCF, the mode characteristics of PCF, sensing applications of PCF long-period grating (PCF-LPG) and PCF Mach-Zehnder interferometer (MZI, PCF-MZI) are investigated in this dissertation. The main achievements of our study have been summarized as following:1. Adjusting PCF dispersion by optimizing structural parameters has been studied based on vectorial effective index method. It is found that zero dispersion wavelength (ZDW) has a dual-extreme characteristic, presenting a maximum value and a minimum value with the variation of air filling factor and scaling parameter, respectively. These discoveries can be used to design PCF with special dispersion curve. Three special PCFs are designed around the 800 nm working wavelength of fetosecond laser, which have flattened anomalous dispersion, normal dispersion and nearly zero dispersion, respectively. Each has a bandwidth about 602. Through numerical modeling, method of writing out PCF-LPG with suitable resonant wavelength by choosing appropriate grating period based on structure parameters is investigated, and also enhancing the inner refractive index (nin) sensitivity characteristic of PCF-LPG by optimizing structural parameters. The nin sensitivity characteristic of PCF-LPG working in antiresonant reflecting optical waveguide is exploited, and it is found that the refractive index sensitivity can reach to 10-7 RIU/pm. A dual-channel method based on PCF-LPG which is able to measure refractive index is proposed and proved, in which medium surrounding PCF-LPG and filled in air holes simultaneously interact cladding mode. Thus, the sensitivity characteristic can be enhanced and refractive index sensor with great sensitivity can be manufactured.3. HE11cl, mode with its dispersive characteristic and nin sensitivity characteristic in PCFs with variant radii are studied. It is found that there are evolving phenomena among ring mode, HE11cl mode, and HE12cl mode with the variation of cladding radius, wavelength and nin, respectively. Several similar modes vary in a similar way with the decrease of cladding radius. The dispersive characteristic and nin sensitivity characteristic are different with different cladding radius, even under the same mode. The dispersive characteristic and nin sensitivity characteristic are changed and enhanced as a whole when the mode order rises. It is found that the nin sensitivity characteristic of PCF-LPG can be enhanced through reducing cladding radius appropriately.4. The factors which can affect the strain characteristic of PCF-MZI are theoretically and experimentally analyzed. The fiber loop mirror strain sensor is made of PCF-MZI. The test results show that the visibility of transmission spectrum can be enlarged, which can reduce bandwidth and improve the precision, with the strain sensitivity of -2.53 pm/με. A large-diameter PCF-MZI with streamline shape splicing region is designed. It is indicated that the strain sensitivity is -1.77 pm/με, however, the refractive index sensitivity characteristic is very weak. Thus, this large-diameter PCF-MZI could be used in index-insensitive strain sensor.5. A large lateral offset structure (LLOS) staged fiber MZI (LLOS-MZI) refractive index sensor is proposed and fabricated. The interference principle, spectrum characteristics and refractive index sensing characteristics are studied. The staged fiber LLOS-MZI sensor owns high refractive index sensitivity. The sensitivity of 327 μm length staged LLOS-PCF-MZI sensor is 2.17*10-7 RIU/pm, and the sensitivity of 436 μm length staged Single mode fiber LLOS-MZI sensor is 3.12*10-8 RIU/pm. And the sensitivity will increase with the decrease of MZI length. The LLOS-PCF-MZI sensor is fabricated. The interference principle and refractive index sensing mechanism are also theoretically analyzed. The refractive index sensitivity of 330 μm length LLOS-PCF-MZI is 6.62* 10-8 RIU/pm. These two kinds of fiber LLOS-MZI are appropriate to make high sensitivity refractive index sensor for rapid measurement.更多还原