基于飞秒激光和塔尔伯特干涉仪制备的Type II光纤光栅阵列及高温传感器

Femtosecond laser phase mask method is suitable for the fabrication of Type II FBG with high-temperature resistance, but it is necessary to solve the serious problems of zero-order optical interference, damage to mask and formation of FBG arrays with different periods. In this project, a new method for preparing Type II FBG arrays in standard silica fiber by femtosecond laser phase mask method combined with Talbot interferometer is proposed. This method can not only effectively suppress the interference of zero-order light on the structure of FBG, reduce the damage to mask, but also fabricate Type II FBG arrays with good repeatability and controllability to realize distributed high-temperature FBG sensor. The main research contents include: by adjusting the time-space characteristics of the optical field, including the chirp of femtosecond pulse and spatial distribution, the influence of laser-induced nonlinear optical effects on beam propagation is suppressed, and the precise control of femtosecond laser targeting is realized; a distributed high-temperature FBG sensor with upper limit working temperature of 1100°C is realized by adopting phase mask method combined with Talbot interferometer to process Type II FBG arrays with different periods in fiber.

飞秒激光相位掩模法适合制备耐高温的Type II光纤布拉格光栅（FBG），但需要解决加工过程中零级光干扰、对掩模版的损伤和形成不同周期FBG阵列的问题。本项目提出一种利用飞秒激光相位掩模法结合塔尔伯特干涉仪在石英光纤中制备不同周期Type II FBG阵列并实现分布式传感的新方法。该方法既能有效抑制激光加工过程中零级光对FBG结构的影响，减少对掩模版的损伤，又可以在光纤上制备重复性和可控性好的不同周期Type II FBG阵列，实现分布式高温FBG传感。项目的主要研究内容包括：通过调控飞秒激光脉冲啁啾、空间分布等光场的时空特性，调节和抑制光诱导非线性光学效应对光束传播的影响，实现飞秒激光靶向的精确控制；利用相位掩模结合塔尔伯特干涉仪，在光纤中制备不同周期的Type II FBG阵列；搭建由光纤光栅解调仪和串接在一起的FBG阵列构成的分布式传感器，可用于1100℃的分布式高温传感测量。

光纤布拉格光栅（Fiber Bragg grating, FBG）温度传感器在传感领域具有广泛应用前景。传统紫外激光适合在光敏光纤中刻写Type I FBG，且光栅的适用温度低于400℃。飞秒激光相位掩模法适合制备耐高温的Type II FBG。本项目利用飞秒激光相位掩模法结合塔尔伯特干涉仪在石英光纤中制备不同周期的Type II FBG阵列，搭建由光纤光栅解调仪和串接在一起的FBG阵列构成的分布式传感器。研究的主要成果：利用飞秒激光微纳加工技术在石英光纤中制备了耐高温FBG微结构，研究了激光功率、聚焦尺寸和曝光时间等加工参数对FBG的制备及其反射率和光谱特性的影响，通过优化激光加工参数，制备出FBG栅区完全覆盖纤芯的高反射率耐高温FBG；研究了耐高温FBG的温度稳定特性，经高温退火后，FBG在1000℃下具有良好的温度稳定性；制备了不同周期的Type II FBG阵列并构建耐高温的分布式传感器，可用于1000℃的分布式高温传感测量。本项目实现的工作温度达到1000℃的分布式耐高温光纤光栅传感器在某些特殊领域和极端环境中具有广泛的应用场景。