飞秒激光写入的光波导机理研究及其应用于海水盐度传感

Planar Light Circuits (PLC) waveguide will be fabricated in silicon-based silica film by using technology firstly. Then the sensing arm of MZI will be written by femtosecond (fs) laser to form 3D MZI structure optical waveguide,which will be used to sense salinity. Three projects will be carried out: .1. The Raman and Atomic Force Microscope will be used to study the effect of the fs laser on the the silicon-based silica molecules. And the physical mechanism of waveguide written by fs laser will be analyzed. .2. The optimized written conditions of optical waveguide in PLC waveguide by fs laser will be fully studied and investigated. By carefully controlling the writing parameters, we will fabricate the optical channel waveguide, whose mode fields will match to these of the PLC waveguide with low loss. By method of near field mode analysis and far filed mode matches, the reason of non-symmetric cross sections of the fs written waveguide will be analysed and field mode matche problesms will be solved. .3. The effect of depth and distance in the sensing arm written by fs laser on the salinity sensitivity will be studied in fabricated 3D MZI optical waveguide sensors. And the high sensitivity of 3D MZI optical waveguide salinity sensors will be fabricated.The salinity sensitivity of the sensor will target at measurement error at ±0.05% range in salt solution concentration. .Those works will expose the physical mechanism of waveguide written by fs laser.Terefore, the interaction between the fs laser and glass can be further explored. Those works will also provide the way to develop some new 3D optical waveguide devices.

本项目首先在硅基二氧化硅薄膜上制作平面光波导（PLC波导），然后在PLC波导中利用飞秒激光写入波导（作为传感臂），制作三维的MZI光波导，应用于海水盐度传感。本项目拟开展三个方面的工作：1. 利用拉曼光谱和原子力显微镜，研究飞秒激光对硅基二氧化硅薄膜分子的修饰作用，探讨飞秒激光写入波导的机理。2. 利用模式分析方法，分析飞秒写入波导截面不对称的原因；探索和控制飞秒激光写入波导的条件，制作出与PLC波导相匹配的低损耗写入波导。3.研究飞秒写入的传感臂的深度和间距对传感灵敏度的影响，设计和制作出高灵敏的三维MZI光波导传感器，海水盐度测量误差控制在±0.05%。通过本项目的实施，理解和掌握飞秒写入波导的机理，为新型三维光波导器件的开发提供指导意义。

海水盐度是海洋动力学以及海洋与大气相互作用中起关键作用的重要参数，它与海水折射率、温度有密切的关系。通过测量海水的折射率和温度特性，就可以评估海水的盐度特性。本项目研究的是高精度光纤传感器。首先采用软件模拟设计出传感芯片结构参数，并利用飞秒激光在硅基二氧化硅上制作光波导，初步确定飞秒写入波导条件（激光能量、透镜的NA、扫描速率），为探索飞秒激光直接写入波导提供技术支持。同时探索了飞秒激光与光刻胶的光聚合方法制作的光波导结构的方法，利用这种方法制作的光波导和空腔结构构成的传感芯片。搭建精细测量平台进行传感特性测量。制作了多种传感器—空腔型不同膜厚度结构，液体封装结构的传感结构等。研究了这些结构的折射率、温度和声波的传感特性，得到了传感灵敏度高达1539.5nm/RIU，877 pm/°C ，900mv/pa。传感灵敏度比传统的光纤传感器具有大幅提高。同时研究了它们在酸性条件、碱性条件和高强度震动等恶劣环境下的传感性能特性，为满足不同恶劣的外部环境提供应用支持。同期进行论文撰写和投稿工作。本项目的研究意义在于可以进一步探索飞秒激光与物质相互作用机理，为利用飞秒激光技术制备的光波导走向实用化奠定理论和实验基础。目前已经开始传感机械封装设计，为传感器的实用化推广奠定基础。