基于飞秒激光直写有源光纤光栅的全光增益控制技术研究

In this project, based on multi-type rare earth doped fibers, we conduct the research on the preparation of active fiber gratings and their functions for gain control by using femtosecond-laser direc-writing technology. According to the theory of all optical gain-clamping, the multi-linear-resonance-cavity is built in amplifiers by means of the prepared gratings. And based on single/dual-FBG scheme, the single-fiber-compacted gain controllers for S-, C- and L-band of erbium-doped fiber amplifiers are investigated in order to balance the performance in terms of gain, flatness and stability. The gain of signals will be simultaneously flattened and clamped because of an accurate control of gain loss. We then conduct the research on gain controllers of the parallel/cascaded broadband (hybrid) fiber amplifiers to realize the joint control of multi-band gain spectra. Further, the technologies of gain control for the Yb/Er-Yb, Bi/Er-Bi, and Nd/Pr doped fiber amplifiers will be studied. And we will focus on the novel transmission and reflection characteristics of the prepared active fiber gratings under the condition of pump induced mechanism with high power. It is believed that, the studied results may extend the applications of gain-clamped fiber amplifiers with high performance due to the enhanced reality and practicality. Also these results may scientifically facilitate the prepared technologies of active fiber gratings based on femtosecond-laser direct writing.

本项目以增益控制为背景，以多种稀土掺杂光纤为研究对象，以飞秒激光直写技术为手段，开展有源光纤光栅的制备与功能化研究。项目以全光增益箝制理论为基础，以平衡增益、平坦度、稳定度三者间性能为目标，利用所制备光栅构造多种线形谐振腔结构，开展基于single/dual-FBG的的单一波段（S、C和L波段）全光增益控制器的单纤集成化研究，精确控制掺铒光纤放大器的增益谱损耗，同步实现多信号光的增益平坦与增益箝制；开展并联/级联结构宽带掺铒（混合）光纤放大器的全光增益控制技术研究，实现多波段增益谱的联合控制；开展镱/铒-镱、铋/铒-铋、钕/镨掺杂光纤放大器的全光增益控制技术研究，探究制备有源光纤光栅在高功率泵浦诱导机制下透/反射谱的新特性。预期研究成果将拓展高性能增益箝制光纤放大器的应用领域，提升其实用性与可靠性，将为丰富飞秒激光制备有源光纤光栅技术提供科学依据。

光纤放大器，尤其是掺杂稀土类光纤放大器在光通信、精密检测与光纤传感等诸多领域有重要应用，其输出光谱的增益平坦度与信号稳定/箝制性对于所在应用场景的性能提升起关键作用。项目组以线性腔掺铒光纤放大器为对象，以飞秒激光直写制备技术为手段，构建了光-电混合增益控制平台，实现了增益信号的平坦度与箝制性能的同步改善，有效提升了增益系统的长、短期工作稳定性能，促进了增益箝制光纤放大器的实用化。项目重点研究了：1) 基于线性腔/环形腔的多波段/多介质光纤放大器的增益控制原理与仿真模型设计；2) 基于飞秒激光直写技术的光纤微结构加工设计与制备实现；3) 基于光电混合增益控制的光纤放大器/激光器的原理与性能优化研究。具体地，布拉格光栅和啁啾光栅构建了宽带激光谐振腔，实现了掺铒光纤放大器输出增益、平坦度、稳定度三者间的平衡，保证了多波长信号的同步增益平坦与增益稳定。结合电子增益控制，引入双通道模糊控制策略，同步监测光谱的波长与强度漂移，显著提升了增益控制放大系统的工作稳定性。掌握了飞秒激光直写制备光纤光栅的技术特征，完成了短周期光栅、长周期光栅，及光纤微腔的制备与优化。项目组基于增益控制放大系统，改善了多波长光纤激光器的工作稳定度；并结合基于模式干涉的梳状滤波器，构建了单/双波长环形腔光纤激光传感器，大幅度提升了系统的检测精度，拓展了相关研究的应用领域与实用性。