基于微结构的干涉型微纳光纤传感机理及其液体辅助飞秒激光制备技术研究

Microfiber optical sensors have attracted more and more attention in recent years because of their advantages of higher sensitivity, faster response, lower power consumption and better spatial resolution compared with the conventional optical fiber sensors. Recently, along with the increasing demands on optical fiber sensors with higher performances and versatilities, spatial miniaturization has been one of the current trends of optical fiber sensors, thus, further work is needed to improve the sensitivity and reduce the size of the sensing structure. The project proposes a novel method to improve the sensitivity and reduce the size of optical fiber sensors by creating a micro-structure in microfiber, and the key technical problem to be solved in the project is how to machine the micro-structure in microfiber with high quality and efficiency. Thus, the technology of femtosecond laser-induced liquid breakdown is employed to fabricate micro-structure in the microfiber. The project will conduct research on three key topics. 1) The proposal needs to study the theory and characteristics of micro-structure microfiber optical sensors, to establish the model of the system, and to analyze the relationship of all parameters. 2) The mechanism, characteristic and application of femtosecond laser micromachining in liquid are studied, meanwhile, the effective techniques and technical parameters can be achieved. 3) Several types of microfiber optical sensors will have been designed to verify this novel sensing method. The success of this project will establish the completed system and bring forward breakthrough to the essential technology, which will contribute to high performance and practical application of microfiber Mach-Zehnder interferometers based on micro-structures.

与传统的光纤传感器相比，微纳光纤传感器尺寸更小，具有更高的灵敏度、响应速度，以及更低的能耗，是当前的研究热点。为了满足光纤传感器高性能化及微型化发展要求，本项目提出一种基于微结构的干涉型微纳光纤传感方法，并利用液体辅助飞秒激光复合微加工技术解决在单根微纳光纤内直写高品质微结构的难题，进一步提高干涉型微纳光纤传感器的灵敏度并优化其尺寸。研究要点包括：1) 研究基于微结构的干涉型微纳光纤传感机理及特性，建立传感理论模型，分析各结构参量与传感性能的内在联系；2) 探索液体辅助飞秒激光复合微加工机理，认识复合微加工工艺对加工性能的影响规律，获得微纳光纤微结构制备的有效工艺及参数；3) 试制几种有代表性的基于微结构的干涉型微纳光纤传感器样件，并通过各种传感实验验证。本项目的成功开展将形成完善的理论体系及若干关键技术，为基于微结构的干涉型微纳光纤传感器高性能化和实用化提供理论及关键技术支持。

为了提高飞秒激光加工精度，顺利帮助碎屑排出，避免液体抖动及光斑漂移的影响，本项目设计液体辅助飞秒激光复合微加工装置，并搭建基于液体辅助飞秒激光微加工平台，理论分析基于液体辅助飞秒激光微加工机理。实验研究液体辅助飞秒激光复合微加工技术参数中激光通量、扫描速度、扫描方式、加工环境、液体深度等参量改变对微纳光纤微结构加工性能的影响规律，获得微结构制备的有效工艺及参数。搭建微纳光纤微加工平台，探索微纳加工光纤拉制工艺参数，拉制出符合项目要求尺寸的微纳光纤，以备批量产出均匀一致的微纳光纤。在普通光纤实验制备微结构温度传感器并进行性能测试，分别测试不同加工介质、不同腔长对温度灵敏度的影响，通过以上实验说明在水中加工的F-P微腔比空气中加工具有较大的优势，相对空气中加工的传感器灵敏度增大了8倍。单孔微结构对比双孔微结构具有较高的温度灵敏度，验证了在激光能量为60 mW、持续时间为5 s时在水中有较好的加工效果，传感器重复性较好，稳定性较高。在前述研究基础之上，本项目在水中实验制备微孔微纳光纤温度传感器，其传感性能相比普通光纤得到大幅上升，与普通光纤传感器相比其尺寸更小，具有更高的灵敏度、响应速度，以及更低的能耗。探索高性能WO3-Pd2Pt-Pt氢敏感薄膜制备工艺，制备特定波长高-低反射率光栅对的光纤氢气传感器，有效提高了氢气传感器的灵敏度和响应速率。