【作者】 戴彬；

【导师】 李进延；

【作者基本信息】 华中科技大学 ， 光学工程， 2020， 博士

【摘要】 微结构光纤凭借结构灵活、性能优异的显著优势在数十年间受到了国内外科学研究者的广泛关注。随着微结构光纤制备和后处理技术的发展和完善,微结构光纤传感也开启了光纤传感领域的全新篇章。微结构光纤的设计制备和后处理对传感性能实现与增强发挥着关键作用。在光纤传感中,光纤模式特性对光纤干涉仪和长周期光栅性能会产生根本影响。微结构光纤可通过结构和材料优化直接实现适用于传感的固有光学特性,微结构光纤后处理则可通过光纤结构物理形变和折射率分布变化增强光纤模式特性。因此,本文的主要工作围绕微结构光纤设计制备、后处理和传感特性研究三方面展开:设计并制备了三种适用于光纤传感的微结构光纤,采用后处理手段增强光纤传感性能,实验研究基于特殊设计和后处理微结构光纤的传感特性。本文首先简要介绍了微结构光纤导光原理及分类、微结构光纤传感器件和微结构光纤后处理技术。从理论分析和以全矢量有限元法为代表的仿真计算方法出发,通过包层几何不对称方法设计了两种结构双折射微结构光纤,实现了单一材料下的光纤高双折射特性;通过中心单一空气孔环形掺杂方式设计了一种环形芯空芯光纤,实现了对模式间干涉和反谐振反射光波导效应的有效抑制;通过包层周期缺失排布方式设计了一种包层缺失型全固微结构光纤,实现了强烈纤芯模式和包层模式在光纤中的共存。采用MCVD离子掺杂技术和堆叠-拉丝技术制备得到了设计结构和光学特性还原度较高的光纤,进行了光纤模式特性相关的验证测试。根据微结构光纤结构和光学特性及传感应用不同,采用以二氧化碳激光加工、液体填充和酸腐蚀处理为代表的微结构光纤后处理技术,对光纤传感性能进行增强。通过热致周期拉锥制备了一种适用于液体填充的空芯长周期光栅,并采用液体填充方法实现了空芯长周期光栅纤芯管理与调谐;通过热致锗元素周期扩散方法制备了一种适用于高温传感的长周期光栅;通过基于氢氟酸腐蚀处理的方法实现了有利于提升折射率传感性能的光纤包层模式倏逝场增强。通过搭建光纤传感实验平台,实验研究了微结构设计和后处理对传感特性的实现与增强效果。在双折射微结构光纤扭转传感与温度响应实验中,混合型和一字型双折射微结构光纤在Sagnac干涉仪中均表现出良好扭转传感特性,其中一字型微结构光纤以1.26×10^-3的高双折射表现出温度不响应特性。在温度传感实验中,液体填充型空芯长周期光栅实现了纤芯模式管理和温度灵敏度增强,最高线性温度灵敏度提升了50余倍,可达-0.618 nm/℃,且可稳定工作于-10℃低温环境。在高温传感实验中,基于高数值孔径光纤的热致元素扩散型长周期光栅经退火处理后,在室温至700℃的反复升温、降温过程中表现出稳定性能,线性温度灵敏度均达0.1 nm/℃。在折射率传感实验中,酸腐蚀处理的包层缺陷型全固微结构光纤在马赫-曾德干涉仪中表现出机械强度良好和温度不响应的折射率传感特性,最高线性折射率灵敏度达2183.6 nm/RIU。更多还原

【Abstract】 By virtue of their flexible structures and excellent performances,microstructured optical fibers have been widely concerned by domestic and overseas scientific researchers for decades.With the development and improvement of fabrication and post-processing technologies of microstructured optical fibers,microstructured optical fiber sensing has opened a whole new chapter in the field of optical fiber sensing.The optimal design,complete fabrication and appropriate post-processing of microstructured optical fibers play significant roles in the realization and enhancement of sensing performances.In optical fiber sensing,fiber optical mode characteristics have fundamental impacts on the performances of fiber interferometers and long period gratings.The intrinsic optical characteristics suitable for sensing can be directly realized through structural and material optimization of microstructured optical fibers,and the optical mode characteristics of fibers can be enhanced through structural physical deformation and refractive index distribution changes of microstructured optical fibers.Therefore,this thesis mainly focuses on three aspects of microstructured optical fibers fabrications,post-processing and research on sensing characteristics:the designs and fabrications of three kinds of microstructured optical fibers suitable for sensing,using post-processing methods to enhance the performances of optical fiber sensing,experimental research on sensing characteristics of the specially designed and post-processed microstructured optical fibers.In this thesis,the light guiding principles and classifications of microstructured optical fibers were briefly introduced.Based on the theoretical analysis and the simulation method represented by the all-vector finite element method,two kinds of birefringent microstructured optical fibers were designed by the cladding geometric asymmetry method,and the high birefringence characteristics of the fiber were realized by single-material fabrication.An annular core hollow fiber was designed by annular doping with a single air hole in the center,realizing the effective suppression of inter-mode interference and antiresonant reflecting guidance effects.A kind of cladding defects type all-solid microstructure fiber was designed by cladding periodically absented arrangement,realizing the coexistence of vibrant core mode and cladding mode in the fiber.Microstructured optical fibers with high designed-structural and optic characteristical reproductions were fabricated by using MCVD-based ion doping technology and stack-drawing technology.According to the structures,optical characteristics and sensing applications of microstructured optical fibers,the post-processing technologies represented by carbon dioxide laser processing,liquid filling and acid etching treatment were adopted to enhance the fiber sensing performances.A kind of hollow core long-period grating was fabricated by thermally-induced periodic tapering,and the core management and tuning characteristics of hollow core long-period grating were realized by liquid filling method.A long-period grating suitable for high temperature sensing was fabricated by thermally-induced periodic diffusion of germanium element.Fiber cladding mode evanescent field enhancement which is beneficial to improve refractive index sensing performance was realized by hydrofluoric acid etching treatment method.By setting up the optical fiber sensing experiment platforms,the realization and enhancement of the sensing characteristics by microstructural design and post-processing were studied.In the experiment of torsional sensing and temperature response of birefringent microstructured fibers,both hybrid and slotted microstructured fibers showed favorable torsional sensing characteristics in Sagnac interferometer,in which the slotted microstructured fiber showed temperature non-response characteristics with 1.26×10^-3high birefringence.In the temperature sensing experiment,the liquid-filled hollow core long-period grating realized fiber core mode management and temperature sensitivity enhancement,and the highest linear temperature sensitivity was increased by more than 50times,up to-0.618 nm/℃,and it can worked stably in the low-temperature environment of-10℃.In the high temperature sensing experiment,the thermally-induced element periodic diffusion long-period grating based on high numerical aperture fiber,after annealing treatment,showed stable performance in the repeated heating and cooling processes from room temperature to 700℃,with linear temperature sensitivity up to 0.1 nm/℃.In the refractive index sensing experiment,the acid-etched cladding-defects type all-solid microstructured fiber showed favorable mechanical strength and temperature non-response refractive index sensing characteristics in mach-zehnder interferometer,with the highest linear refractive index sensitivity of 2183.6 nm/RIU.更多还原