微纳光纤中声致周期结构的耦合特性及应用研究

By introducing acoustic wave into micro/nano optical fiber, the project highlights the fast response and convenient tunablitiy for the structure, which is important for the application of micro/nano photonics devices. In the project, we expect the acoustic wave will bring periodic refractive index modulations in the micro/nano optical fiber. Based on up to data researches, such structure should gain the features of tunable, fast response, low power consumption, compact size, and so on, yet few works has been done in the field. Our project will include three parts covering from the fundamental theory to its possible applications: 1. Theoretical analysis the characteristics of periodic refractive index modulation produced by propagating acoustic wave in micro/nano fiber to present the parametric influence to the micro/nano fiber, including diameter, refractive index, acousto-optic coupling length and so on. 2. Experimentally explore the characteristics of acousto-induced periodic structure to convince the theory, and more important, achieving the tunability of spectral, driving power features, mode coupling, response time, and so on for its further applications. 3. With a fixed period grating structure driven by acoustic wave, we expect to construct acosuto-optic superlattice structure in the micro/nano optical fiber and explore its applications such as tunable subluminal device. The project will present a clear view to acousto-optic effects in the micro/nano scale, meanwhile it will introduce characteristics of tunability with fast response to all-fiber micro/nano photonics devices, which is important for its application.

微纳光纤中声致周期结构的构建是使光纤光栅具有便捷可调谐特性的一个重要途径，它的实现有助于便捷可调谐微纳光子学器件的制作及应用。本项目旨在如何利用微纳光纤中超声波的传输来诱导周期性结构，进而使其具有可调谐、快响应、低功耗、微型化等特性。主要研究内容有：1、理论分析超声波在微纳光纤中传输时所诱导周期性折射率调制的特性，并给出超声波（模式、功率、频率）和微纳光纤（直径、折射率、材料声速、声光耦合长度）的参数特性对声致周期性折射率调制的影响；2、实验研究声致周期结构的光谱可调谐特性、功耗特性、模式耦合特性、时间响应特性等；3、在微纳光纤中，把声致周期结构和固定周期的光栅结构相结合，构建复合调制周期结构，并利用其色散特性实现可调谐慢光结构。本项目的开展有助于加深人们在微纳尺度范围内对声光效应产生更为清晰的认识，同时也为构建具有便捷可调谐和快响应特性的微纳光子学器件提供一种方法。

本项目旨在利用超声波在光纤中的传输诱导声致光栅结构，进而探索声致光栅结构在光外差测量技术、光纤中结构光场产生及调控等方面的应用，本项目完成的主要内容：①利用声弯曲波在光纤上的传输构建了声致光栅结构，利用锥形微纳光纤与声致光栅结构之间的耦合构建了全光纤光外差频移器，在此基础上实现了全光纤光外差精密测量系统的构建及微振动解调程序编写，并实现了皮米级微振动精密测量；②基于声致光栅的折射率分布，建立了光纤中矢量模式耦合理论模型，利用声致光栅实现了光纤中柱状矢量光场的高效产生及调控；③建立了光纤中声致光栅结构实现矢量模式耦合的全矢量理论模型，对光纤中矢量模式间的耦合进行了定量计算，并在实验上实现了通讯波段可调谐涡旋光场产生；④建立了光纤中高阶涡旋光场产生的级联矢量模式耦合理论模型，并利用声致光栅实现了光纤中高阶涡旋光场的产生及拓扑荷调控；⑤利用声纵波驱动光纤布拉格光栅构建了声致复合光栅结构，并利用声致复合光栅结构构建了全光纤光外差精密测量系统，实现了纳米级精度测量。本项目的研究工作有助于研究者们对光纤中声致光栅结构的产生机理及构建方法产生更为清晰的认识，并为构建全光纤频移器及矢量/涡旋模式产生等具有便捷可调谐特性的微纳光子器件提供一种方法。