基于光纤内微腔液滴振动的声—光调制特性研究

In this project,we will mainly investigate the vibration characteristics of nanoliter liquid drop sealed in optical fiber stimulated by acoustic wave. And mechanism of acoustic-optical interaction and modulation will be given based on the vibration characteristics of the liquid drop, which provides theoretical bases and practical methods for highly sensitive detection of ocean acoustic wave with wide range of frequencies. First, we will design and create the micro-channel with diameter of 10-20μm and nanoliter micro-cavity in the fiber based on the theoretical model of femtosecond laser induced water-breakdown. By arc discharge, the liquid drop will be sealed in the optical fiber micro-cavity.Then, by use of the lattice boltzmann theory, the spacial distribution in shape and characteristic mode of vibration of the liquid drop in optical fiber micro-cavity will be fully studied under the stimulating acoustic wave with different frequency and intensity. Finally, we will establish and optimize a theoretical acoustic-optical interaction and modulation model in the proposed integrated micro-fluidic structure by investigating the effects of size, shape, and vibration modes of the liquid drop stimulated by acoustic wave on optical signal in order to improve the acoustic-optical modulation sensitivity.This project aims at solving problems in the integration of micro-fluidic structures and optical fiber, breaking through the bottleneck of narrow response frequency and low sensitivity for acoustic wave response based on the vibration of fiber itself, and realizing highly sensitive detection of ocean acoustic wave with wide range of frequencies.

本课题主要研究密封在光纤内纳升量级的液滴在声波作用下的振动特性，并基于液滴的振动提出一种新的声-光调制机理,为海洋声波的宽频率、高灵敏探测提供理论与技术支持。首先，根据飞秒激光诱导水击穿的理论模型，设计并刻蚀出直径为10-20微米的光纤微流体通道和容积为纳升量级的光纤微腔，并辅以电弧放电将液滴密封在光纤微腔内。然后，根据晶格波尔兹曼理论，研究不同液体在光纤微腔内形成的液滴的空间形态分布，以及液滴在不同强度和频率的声波作用下的振动模式。最后，研究光纤内微腔液滴在声波作用下的体积、形态和振动对光纤内光信号的影响，建立并优化基于光纤内微腔液滴振动的声-光调制模型,提高声-光调制灵敏度。本课题旨在解决微流体结构与光纤集成的问题，突破光纤本身响应声波振动频率窄、灵敏度低的瓶颈，从而实现对不同频率与强度的海洋声波信号的高灵敏度探测。

光纤水下声波传感探头能够将水下声压信号转换为光纤应力变化，但由于固体本身响应声波振动比较微弱，因此限制了光纤声—光调制的实际应用。将微量液体引入并密封在光纤内，能够利用液体随声波的振动对光纤内的光信号进行调制，大幅提高声波传感灵敏度。本课题建立了飞秒激光诱导水击穿空腔刻蚀模型，在光纤内设计并制备出了能够填充密封液体的光纤微腔与微通道结构。成功地分别将纳升量级蒸馏水和乙醇填充并密封到光纤微腔内，实验研究了不同体积的蒸馏水和乙醇在光纤微腔内的空间分布情况，结果表明蒸馏水和乙醇会吸附在微腔内壁，从而在微腔中部形成能够运动的气泡。建立了光纤微腔内气泡在声波作用下的受迫振动模型和基于光纤微腔内气泡的干涉调制模型，研究了声波导致的气泡振动对光纤微腔结构干涉光谱的影响。在实验室内搭建了光纤声波探测系统，对光纤微腔结构的声—光调制特性进行了测试，实现了对水下声波的高灵敏传感探测。此外，利用项目研究过程提出并优化的光纤微腔制备与液体填充密封方法，设计并制备出了其他用于温度、应变、角度、液体折射率等参数高灵敏传感探测的光纤微腔结构，在精密仪器制造、生物化学、海洋环境监测等领域具有重要应用潜力。本课题解决了微流体结构与光纤集成的问题，突破了光纤材料本身作为调制基元传感灵敏度低的瓶颈，提出了一种更加有效的光纤信号调制方法，为光纤传感探头的制备和应用提供了新的思路。基于本项目研究成果，申请发明专利3项，发表SCI 论文22 篇，其中，在国际光学一流期刊（Optics letters、Optics Express、Photonics Research、Sensors and Actuators B，SCI 影响因子均大于3.0）上发表论文8篇。