2.7微米抗辐射掺铒单晶光纤的制备及高性能级联激光技术研究

Erbium-doped GYSGG series of mid-infrared laser crystals operated at 2.7 μm have excellent radiation resistant properties, and thus have important applications in the fields of strong radiation environment, medicine, scientific research and national defense. Many applications also require crystals to possess excellent laser performance with high efficiency, high repetition rate and high beam quality. However, both the thermal lens effect of the general laser crystal element and the long lifetime of the lower level 4I13/2 of Er3+ ions affect the improvement of 2.7 μm laser performance. In this project, we propose that the use of single crystal fiber to enhance thermal management. At the same time, the level coupling is combined with cascaded lasers, which it is not only can weaken the adverse effect to the 2.7 μm laser output because of the long level lifetime, but also the concentration of Er3+ can be decreased greatly, thereby further to reduce the damage of pumping end-face and laser threshold, improve efficiency and repetition rate.. By investigating the influence of the melting zone interface on the growth stability and optical quality of single crystal fibers, the growth parameters are constantly optimized and growth mechanism and rules are mastered, the high quality single crystal fibers are obtained. The radiation resistant micro-mechanism is revealed and the model is proposed. The concentrations of the activation and the level coupling ions, fiber diameter and length would be optimized through level lifetime and laser performance feedback. To design and optimize the cascaded laser cavity structure, and achieve mid-infrared laser with low threshold, high efficiency, high repetition rate in order to meet space radiation environment applications.

2.7μm掺铒GYSGG系列中红外激光晶体具有优良的抗辐照性能，在强辐射环境、医学、科研和国防等领域有重要应用，许多应用还需要晶体具有高效、高重频及高光束质量的激光性能。但通常激光晶体元件的热透镜效应以及Er3+下能级寿命较长，限制了2.7μm激光性能的进一步提高。本项目提出采用单晶光纤加强热管理，同时将能级耦合与级联激光相结合，不仅能改善下能级寿命较长对2.7μm激光输出的不利影响，而且掺Er3+浓度可大幅降低，从而进一步减小泵浦端面损伤、降低激光阈值、提高效率和重频。.通过研究熔区界面等对单晶光纤生长稳定性及光学质量的影响，不断优化生长参数，掌握生长机理和规律，获得优质单晶光纤；揭示抗辐射微观机理和提出模型；通过能级寿命、激光性能反馈优化出最佳的激活及能级耦合离子浓度、光纤直径及长度；设计优化级联激光谐振腔，实现低阈值、高效率及高重频的中红外激光，满足空间等强辐射环境下应用的需要。

2.7μm掺铒GYSGG系列中红外激光晶体具有优良的抗辐照性能，在强辐射环境、医学、科研和国防等领域有重要应用，许多应用还需要晶体具有高效、高重频及高光束质量的激光性能。但通常激光晶体元件的热透镜效应以及Er3+自终止效应限制了2.7μm激光性能的进一步提高。本项目中，我们提出采用制备Er,Pr:GYSGG单晶光纤的方法加强增益介质的热管理性能以及采用级联激光的方法降低Er3+自终止效应。按照四年研究计划开展了单晶光纤制备、质量检测、激光性能表征及级联实验平台搭建等工作，制备了Er:YSGG、Er,Pr:GYSGG单晶光纤和1at.%Er:YSGG晶体，对单晶光纤的直径波动、传输损耗、抗辐照特性进行了研究，通过Comsol软件模拟了单晶光纤在半导体激光器端泵模式下的热分布，并采用970nmLD端面泵浦单晶光纤获得了2.7μm高光束质量和优异抗辐照特性的中红外激光输出。另外，我们研究了962nmLD端面泵浦1at.% Er:YSGG级联脉冲激光器，结果表明级联技术有助于 2.7μm激光斜效率的提升。因此，将单晶光纤的制备和级联激光的采用相结合是一种实现低阈值、高效率及高重频的中红外激光输出的有效方法，在晶体的浓度优化及光纤包层的制备等方面值得进一步深入研究。