探针式空芯光纤耦合回音壁模微腔及其传感与激光特性研究

Due to its ultra-high Q factor and small mode volume, the whispering gallery mode microcavity is the important building block for high sensitive sensors and low threshold lasers. Compared with the traditional direction-pass coupled microcavity, we proposes a probe-like hollow core fiber coupled whispering gallery mode microcavity to form a reflective integrated fiber device, with its sensing and lasing properties studied in detail. There are three aspects included in the proposal. Firstly, we will establish the theoretical model of the device based on the mode theory, the beam propagation method, the coupled mode theory, the transfer matrix method, and the energy-level rate equation. Theoretical study on the characteristics of the mode coupling between the tapered fiber and hollow core fiber, the hollow core fiber and microcavity, and the total performance of the fiber device will be carried out. To fabricate the device, the fiber drawing tower, three-dimensional micro-nano controlling platform, fusion splicer and CO2 laser are used. We will also explore the methods to optimize the process in order to improve the performance of the device. Finally, the sensing and lasing characteristics of the device will be experimentally carried out, with the performance enhancement also studied. The proposed probe-like hollow core fiber coupled whispering gallery mode microcavity has universal significance for the novel coupled microcavity, which also has important theoretical expansion on microcavity and important application potentials in sensing and lasing.

回音壁模微腔由于具有超高Q值、较小模式体积等优点，是实现高灵敏传感器和低阈值激光器的重要载体。相比于传统的直通式耦合微腔，本课题提出一种探针式空芯光纤耦合回音壁模微腔的反射式集成光纤器件，并系统研究其传感与激光特性。主要工作包括三个方面：基于模式理论、光束传播法、耦合模理论、传输矩阵法和能级速率方程建立器件理论模型，理论研究微纳光纤融锥—空芯光纤、空芯光纤—微腔的耦合特性和器件整体特性；通过光纤拉丝、三维微纳操控、放电拉锥、二氧化碳激光微焊接等工艺实验制备器件，探索优化制备工艺以改进器件性能；最后实验研究探针式器件的传感和激光特性，并研究器件性能改善方案。本项目所研究的探针式空芯光纤耦合回音壁微腔对新型微腔耦合结构具有普遍意义和推广价值，是对微腔研究的重要拓展，也将在传感和激光领域具有重要应用前景。

通过微腔内壁上的光学全反射，回音壁模微腔能将光能量低损耗地局域在小模式体积内，具有高Q值和高能量密度，是实现高灵敏度传感器和低阈值激光器的重要载体。相比于传统的直通式耦合结构，本课题提出了一种输出端和入射端统一的空芯光纤耦合回音壁模微腔器件，实现反射式集成光纤器件结构，具有探针式结构，系统研究了其传感和激光特性。本项目主要开展三个方面的研究：1）空芯光纤谐振机理及传输特性研究，包括石英毛细管MMI和FP传感器研究和三段式结构谐振机理研究；2）回音壁模无源微球耦合空芯光纤器件研究，包括腐蚀小内径毛细管回音壁模式耦合器、拉锥大内径环芯空芯光纤回音壁模式耦合器、双悬芯空芯光纤回音壁模式耦合器、大内径毛细管zigzag回音壁模式耦合器和实验发现光纤端面能激发微柱腔轴向模式并与局域模式干涉；3）回音壁模有源微球耦合空芯光纤器件研究，包括有源微球与空芯毛细管的耦合模型、铒/镱离子掺杂微球耦合系统的速率方程及实验测试，毛细管壁厚和微球半径对阈值功率与斜率效率的影响研究。本项目所提出的一系列探针式空芯光纤耦合回音壁模式微腔器件结构对新型微腔耦合结构具有普遍意义和推广价值，是对微腔研究的重要拓展，也将在传感和激光领域具有重要应用前景。