面向空间应用多重场效应下的高功率Yb石英光纤耐辐照机理研究

Ytterbium-doped silica fiber lasers offer a very attractive technology to implement space laser radar, space trash disposal and space laser weapon, owing to their reduced weight, size, and high electronic-optic efficiency. However, the radiation-induced attenuation of a rare-earth (RE)-doped active fiber is approximately 1000 times of that of a passive (RE-free) fiber under the same radiation condition. It poses a severe challenge to the long-term stability of ytterbium fiber laser in space. This project is focused on the mechanism research of radiative-induced darkening (RD) of ytterbium doped silica fiber (YDF). The ytterbium doped silica glasses co-doped with different elements (Al, P, Ce, F et al.) will be prepared by using sol-gel combining high temperature sintering method. In order to modulate the refractive index profile of fiber core and the local environment of Yb3+ ions, the YDF preform will be prepared by MCVD combining with multi-steps soaking with multi-elements doped sol-solutions. Using a combination of experimental techniques, such as cw and pulsed EPR, solid-state NMR as well as other spectroscopic methods, on-line fiber laser testing platform with multi-field effects simulating those of space environments, we will study in details the dynamic evolution of atomic level micro-structures and color centers in the process of radiative-induced darkening of ytterbium doped silica glass and its fiber. Based on this research, the fiber core composition, fiber structure, and fiber pre-treatment method can be optimized. The model for radiation-induced defect generation and annihilation will be proposed. It will provide a system solution to solve the problem of RD in YDF and theoretical basis for the fabrication of high performance radiation-resistive YDF for space application.

掺镱石英光纤激光器具有重量轻、体积小、电光转换效率高等优点，在空间激光雷达、太空垃圾处理及军事等方面有重要应用价值。然而，稀土掺杂有源光纤在太空辐射环境中的辐射诱导损耗是非稀土掺杂无源光纤的1000倍，这对空间应用Yb光纤激光器的长期稳定性带来严峻挑战。本项目以Yb石英光纤辐致暗化机理研究为主线，采用溶胶凝胶结合高温烧结法制备含不同共掺元素（Al,P,F,Ce等）的Yb石英玻璃。采用MCVD结合溶胶液分步多层浸泡沉积制备Yb光纤预制棒，实现纤芯折射率和Yb3+离子局域环境调控。应用连续及脉冲波EPR、固态NMR等结构和其它光谱分析手段，搭建模拟空间辐射环境及温度等多重场效应的激光性能在线测试平台，研究掺Yb石英玻璃及光纤在辐致暗化过程中原子级结构缺陷演化过程；获得纤芯成分、光纤结构及光纤预处理的优化设计方案；建立辐射诱导缺陷产生与湮灭模型；提出空间应用Yb石英光纤辐致暗化问题的系统解决方案

掺镱石英光纤（YDF）激光器具有重量轻、体积小、电光转换效率高等优点，在空间激光雷达、太空垃圾处理及军事等方面有重要应用价值。太空电离辐射诱导YDF损耗增加、增益性能下降是当下急需解决的关键科学问题。本项目以提高YDF的耐辐照性能为主要目的，同时兼顾其激光性能，重点研究YDF辐致暗化的产生机理和抑制方法。采用溶胶凝胶法结合真空烧结法制备含不同共掺元素（Al、P、Ge、Ce、F、B）的YDF纤芯玻璃。对玻璃样品热退火或热淬火处理，以改变其热历史。系统研究玻璃组分和热历史对YDF芯玻璃折射率和光谱性质的影响规律及其机理，为获得优异的YDF纤芯成分和制备工艺奠定基础。采用193nm激光器、X射线、γ射线作为辐照源，并采用电子顺磁共振、核磁共振、拉曼等结构研究方法从Yb3+离子局部结构、玻璃网络近中程结构、辐射诱导点缺陷等原子级微观尺度出发，系统研究了YDF纤芯玻璃的辐致暗化机理。从源头上找到提高YDF耐辐射性能的解决方案。采用MCVD结合溶胶液分步多层浸泡掺杂制备YDF预制棒，实现纤芯折射率分布和Yb3+离子局域环境调控的统一。发明了一种基于预制棒预处理的抗辐照加固处理新方法，进一步提高YDF耐辐照特性。搭建模拟太空辐射环境的激光性能离线和在线测试平台，系统研究了纤芯成分、抗辐照加固处理条件、辐射环境对YDF激光及耐辐照特性的影响规律和机理。为研制高增益、耐辐照YDF提供理论依据。本项目执行期间共发表论文37篇，申请专利5项，培养博士研究生4名。出版专著一部——“稀土掺杂石英光纤及应用”。该项目的研究工作为所在课题组承担GF某重点项目并成功研制耐辐照高功率掺镱石英光纤奠定了重要基础。