高效中红外荧光发射的钬、钕共掺氟化铅激光晶体生长与性能研究

Mid-infrared (MIR) lasers operating around 3.9 μm have attracted much attention for numerous applications in environment and military fields. Ho3+ doped crystals are well-known laser materials with transitions in the MIR region around 3.9 μm (5I5→5I6). However, the 3.9 μm emission cannot be obtained efficiently due to (i) the lack of commercialized laser diodes (LD) corresponding to the intrinsic absorption of Ho3+ ions, (ii) the fluorescence lifetime of the upper 5I5 level is considerably shorter than that of the lower level 5I6, and (iii) the host material with high phonon energy. To solve these problems, we have found that Nd3+ ion was demonstrated to be an effective sensitizer for Ho3+ ion, and a deactivated ion to greatly reduce the lifetime of 5I6, and increase 3.9 μm emission in Ho3+:PbF2 crystal, which has a low phonon energy about 250 cm-1. As we know, these works has not been reported at home and abroad, and on this basis, we would further carry out the research on the growth and optical properties of Ho3+, Nd3+ codoped PbF2 crystal in our project, 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 novel Ho3+/Nd3+:PbF2 MIR laser crystal with excellent properties will be obtained to carry on LD pumping and high efficient 3.9 μm fluorescence-emission, which would lay the foundation for the develop of novel MIR laser materials with excellent properties, and the improvement of MIR laser technical merit.

3.9微米中红外激光在环境、军事等领域有着重要的应用前景。Ho3+掺杂晶体是该波段备受关注的激光材料，然而不能直接使用激光二极管(LD)泵浦、下能级寿命远远长于上能级寿命、晶体声子能量高等瓶颈限制其广泛应用。我们通过在低声子能量Ho3+:PbF2晶体(250cm-1)中引入对Ho3+离子具有敏化与退激活双重作用的Nd3+离子，使晶体既适合LD泵浦，又能降低下能级荧光寿命、增强3.9微米荧光发射。目前该方面的工作国内外尚未有报道，本项目将进一步开展Ho3+,Nd3+共掺PbF2晶体制备及其中红外光学性能的研究工作，进行晶体制备工艺优化、掺杂离子浓度优化、Nd3+对Ho3+敏化与退激活双重作用机理探索、激光性能评估等方面的系统研究，获得兼具LD泵浦和高效3.9微米荧光发射的Ho3+/Nd3+:PbF2新型中红外激光晶体，为发展性能优异的新型中红外激光材料和提高中红外激光技术水平奠定一定的基础。

3.9微米中红外激光在环境、军事等领域有着重要的应用前景。Ho3+掺杂晶体是该波段备受关注的激光材料，然而不能直接使用激光二极管(LD)泵浦、下能级寿命远远长于上能级寿命、晶体声子能量高等瓶颈限制其广泛应用。本项目通过在低声子能量Ho3+:PbF2晶体(250cm-1)中引入对Ho3+离子具有敏化与退激活双重作用的Nd3+离子，使晶体既适合LD泵浦，又能降低下能级寿命、增强3.9微米荧光发射。具体进行晶体制备工艺优化、掺杂离子浓度优化、Nd3+对Ho3+敏化与退激活双重作用机理探索、激光性能评估等方面的系统研究。. 取得重要结果有：自主设计双规运行坩埚下降炉，利用该设备，成功制备尺寸达到Ф30mm×50mm的Ho/Nd:PbF2新型中红外激光晶体，晶体质量良好，没开裂及散射颗粒；成功实现敏化和退激活双效作用，获得增强的3.9微米荧光发射；对Ho和Nd浓度进行优化，发现当Ho和Nd浓度比例为1:1时，获得较优的荧光发射性能；进一步地，对Ho和Nd之间的能量传递机制进行分析和研究，发现它们之间除了明显的敏化和退激活作用之后，还存在复杂的交叉弛豫和激发态吸收，其中部分过程有利于3.9微米荧光发射，然而更具体的作用机制还需下一阶段的研究。项目执行期间共发表8篇SCI收录论文，同时获得6项授权发明专利。. 综上所述，本项目获得兼具LD泵浦和高效3.9微米荧光发射的Ho/Nd:PbF2新型中红外激光晶体，取得自主知识产权，为发展性能优异的新型中红外激光增益材料和提高中红外激光技术水平奠定一定的基础。