新型3微米钬镨共掺氟化物激光晶体研究

Fluoride crystals, such as LuLiF4、YLiF4、BaY2F8, are the excellent mid-infrared laser crystals with low phonon energy, good physical, chemical, mechanical, and thermal properties. The 2.7-3.0 micrometer (Ho3+:5I6→5I7) lasers can be realized in the Ho3+ doped fluoride crystals, which has important applications in the medicine, military, and scientific fields. However, the 2.7-3.0 micrometer laser cannot be obtained efficiently due to the self-terminating "bottleneck" effect of Ho3+:5I6→5I7, which may result from the fluorescence lifetime of the lower 5I7 level is considerably longer than that of the upper level 5I6. To solve this problem, we have found that the Pr3+ ion was demonstrated to be an effective deactivated ion for Ho3+ ion to greatly reduce the lifetime of 5I7 in our early experiments, which can suppress effectively the self-terminating "bottleneck" effect, lower the laser threshold, and improve the laser output efficiency. In this project, we would carry out the research on the growth, optical properties, and laser performances of Ho3+, Pr3+ codoped fluoride crystals (LuLiF4、YLiF4、BaY2F8), the emphasis is to improve the process of crystal growth, optimize the concentrations of doped rare earth ions, explore the mechanism of fluorescence, and evaluate the laser performance. Finally, a kind of excellent Ho3+, Pr3+ codoped fluoride (LuLiF4、YLiF4、BaY2F8) MIR laser crystals independent intellectual property will be obtained, which would establish a foundation for the application of 2.7-3.0 micrometer Ho3+ lasers.

氟化物晶体（LuLiF4、YLiF4、BaY2F8)声子能量低，具有良好的物化、机械和热学性能，是综合性能优良的中红外激光基质晶体，掺Ho3+的氟化物晶体可以实现2.7-3.0微米激光输出，在医疗、军事、科研等领域有着重要的应用前景。然而Ho3+:5I6→5I7跃迁是自终止过程，下能级5I7寿命远远长于上能级5I6寿命，制约激光输出，限制其广泛应用。我们初步实验表明，通过引入对Ho3+离子具有退激活作用的Pr3+离子，能够降低下能级5I7荧光寿命，有效抑制自终止效应，降低激光阈值，提高激光输出效率。本项目将开展Ho3+、Pr3+共掺氟化物（LuLiF4、YLiF4、BaY2F8)激光晶体的生长、光谱和激光等性能研究工作，通过晶体制备工艺优化、掺杂离子浓度优化、发光机理探索、激光性能评估等方面的系统研究，获得具有自主知识产权的新型高效激光晶体，为2.7-3.0微米的激光应用奠定基础。

2.7~3.0微米中红外激光在大气污染监控、医疗、太空、光电对抗、反恐等民用和军用领域具有十分广泛的应用前景。面向新型高光学质量稀土离子掺杂氟化物激光晶体，本项目开展了Ho、Pr、Er、Tm等稀土离子掺杂LLF、YLF、BYF、LaF3和CeF3晶体的结构、分凝、光学性能、发光机理、掺杂离子浓度优化、激光性能评估及实验等研究工作，主要内容包括：.Ⅰ：研究了中红外氟化物激光晶体的生长工艺。采用坩埚下降法和提拉法生长稀土离子掺杂氟化物激光晶体，优化晶体生长工艺技术，克服晶体中散射、开裂、失透、包裹、孪晶等问题，获得晶体生长关键工艺参数，成功生长出高光学质量的氟化物系列晶体。.Ⅱ：研究了中红外氟化物激光晶体的物化和光谱性能。测试了激光晶体的吸收光谱、荧光光谱、荧光寿命等，研究晶体的吸收、荧光发射等光学性能，进行了Judd~Ofelt理论计算，通过辐射寿命、自发辐射几率、荧光分支比等参数评估了晶体的光谱性能及激光性能。.Ⅲ：研究了中红外氟化物激光晶体的激光性能。根据激活离子的光谱特性和能级结构特征，选择合适的泵浦源，研究了氟化物激光晶体的激光泵浦光谱特性；开展了相应的激光晶体激光实验，设计和优化晶体元件、泵浦谐振腔系统以及光学耦合模块，获得中红外波段激光输出，研究激光光谱特性，并针对不同激光晶体的激光输出特性，评估了应用前景。.面向高光学质量激光晶体，本项目研发出多种具有自主知识产权的Ho/Pr/Er等掺杂氟化物激光晶体，包括：Ho,Pr:LuLiF4、Ho:BaY2F8、Ho,Pr:LaF3、Yb,Ho:LaF3、Nd,Ho:LaF3、Nd,Er:LaF3晶体，其中，Ho,Pr:LuLiF4、Ho:BaY2F8的晶坯尺寸均大于30×45mm3。基于本项目的研究内容与成果，发表标注资助号的SCI收录文章20篇，申请国家发明专利3项，培养3名博士研究生，本项目的研究成果，对于发展新型中红外激光应用和提高中红外激光技术水平具有重要意义。