基于非对称表面芯双芯光纤集成式干涉仪的生物传感技术研究

Aim at problems of the present fiber biosensors such as low sensitivity, poor mechanical strength and complex fabrication process; we propose a novel optical fiber biosensing technique based on an asymmetric surface twin-core fiber. One core of the twin-core fiber is designed at the interface of the fiber cladding and air to obtain strong evanescent wave, which solve the problems that for the traditional fiber biosensors, to get strong evanescent wave part or all of the cladding have to be removed using side-polishing or chemical etching method. The other core is located at the axis of the fiber acting as reference beam, and constructing an integrated in-fiber interferometer together the surface core. Therefore the concentration change of the tested sample can be detected from the variation of the phase difference between the surface core and the central core. Such a device has a higher sensitivity than the traditional evanescent wave type fiber biosensors. Meanwhile its interference spectrum which is achieving from the fundamental core mode of the central core and the surface core is better than the other interferometric biosensor whose interference spectrum is obtained from the core mode and the cladding modes. The biosensor proposed in the project has advantages such as high sensitivity, good mechanical strength, easy to fabricated and low cost. We expect we can provide a new detecting method and technical approach for the field of optical fiber biosensors, which has scientific significance and practical application value for promoting the development of the optical fiber biosensing technology.

针对现有光纤生物传感器灵敏度低、机械强度差、制作工艺复杂等问题，本项目提出了一种基于非对称表面芯双芯光纤的光纤生物传感技术。通过将光纤的一个纤芯设计在光纤包层与空气的界面处直接获得较强的倏逝场，解决了传统光纤生物传感器需要对光纤包层进行抛磨、腐蚀等处理才能获得较强倏逝场的问题；通过在光纤轴心设置另一个纤芯作为参考光路，构建集成式光纤干涉仪，将被测样品浓度的变化转换成光相位的变化进行测量，具有比传统的倏逝场型光纤传感器更高的测量灵敏度，同时又解决了目前模间干涉型（纤芯模与包层模）传感器干涉光谱多为多模干涉的问题。本项目提出的生物传感器具有灵敏度高、机械强度好、制作简单和成本低的优点。通过本项目的研究，为光纤生物传感领域提供一种全新的检测方法和技术手段，对促进光纤生物传感技术的发展具有重要的科学意义和应用价值。

面向生物、化学检测领域对微小型、高灵敏度在线传感器的迫切需求，本项目开展了基于多芯结构的光纤生物传感器的研究。项目的主要研究内容包括：1）基于热扩散效应的双芯光纤耦合器的设计与制作；2）双芯环形芯光纤的传输特性分析及参数优化，对双芯环形芯光纤的环形芯内壁直径和环形芯厚度对分光比和传输损耗的影响进行了系统的分析；3）单模光纤与双芯环形芯光纤的连接耦合理论分析，研究了耦合锥区参数对双芯环形芯光纤两芯之间分光比的影响；4）单模光纤与双芯环形芯光纤的连接耦合实验研究；5）基于双芯环形芯光纤的干涉仪制作和传感特性测试，包括双芯环形芯光纤Mach-Zehnder干涉仪和Michelson干涉仪的制作和传感特性测试；6）双芯环形芯光纤表面生物敏感膜的制备；7）双芯环形芯光纤干涉仪的葡萄糖检测；8）基于七芯光纤锥的超高灵敏度折射率传感特性研究。在项目执行期间，取得的重要研究成果有：1）发展了一种基于热扩散效应的新型多芯光纤耦合器，解决了传统锥形双芯光纤耦合区机械强度低，对温度、应变和折射率敏感，封装尺寸大等问题，为制作基于多芯光纤集成干涉仪这类传感器提供了更加可靠、稳定的技术方法；2）发展了一种基于七芯光纤细锥的超高灵敏度折射率传感器，该传感器的折射率灵敏度可以达到104 nm/RIU，为生物、化学传感领域的微量或痕量检测提供一种有效的技术手段。