不同工艺制备的低掺镁近化学计量比铌酸锂晶体缺陷结构及其对性能的影响研究

Near stoichiometric lithium niobate (nSLN) ferroelectric superlattice is an important material employed in tunable all-solid-state laser and THz wave based on quasi-phase matched technique. It is difficult to prepare nSLN crystals due to non-congruent composition. There are many researches on preparation of nSLN crystals, and crystals prepared by Li-rich melt growth method and diffusion method have been put into use, but performances of nSLN crystals prepared by different techniques have great differences, which limits applied research. Moreover, the lattice defect and its impact on performance of nSLN crystals prepared by different techniques are short of systematic research, which restricts further development of preparation of practical nSLN crystals..Aiming at the requirement of low-magnesium-doped nSLN crystals for application in mid-infrared based on QPM-OPO technique, this project will systematic study on lattice defect structure of nSLN crystals prepared by different techniques, analyze the formation mechanism of lattice defect, study comparatively nonlinear effect, photorefractive effect and ferroelectric domain inversion of different crystals, then explore structure-function relationship in low-magnesium-doped nSLN crystals. The preparation process of nSLN crystals would be optimized, and the foundational problems encountered in application and preparation of practical nSLN crystals would be resolved through the research work of this project.

近化学计量比铌酸锂（nSLN）铁电超晶格是基于准相位匹配技术的可调谐、全固态激光器及太赫兹光源的重要材料。由于nSLN晶体是非固液同成分共熔配比晶体，导致其制备较困难。关于nSLN晶体制备的研究很多，且富锂熔体生长和扩散法制备的晶体得到了一定应用，但不同工艺制备的晶体性能存在较大差异，限制了晶体应用的研究，另外不同晶体晶格缺陷结构及其对晶体性能的影响机制等基础问题缺乏系统研究，制约了实用化nSLN晶体制备的进一步发展。.本项目围绕中红外QPM-OPO用低掺镁nSLN晶体，系统研究富锂熔体生长和扩散法制备的不同晶体晶格缺陷结构，结合制备过程分析晶格缺陷形成机制，对比研究两类晶体的非线性效应、光折变效应和铁电畴反转特性等，进而探索低掺镁nSLN晶体的“构-效”关系，以期指导nSLN晶体的制备工艺优化，解决目前实用化nSLN晶体应用和制备所面临的基础性问题，为实用化nSLN晶体的制备奠定基础。

近化学计量比铌酸锂（nSLN）铁电超晶格是基于准相位匹配技术的可调谐、全固态激光器及太赫兹光源的重要材料，但不同工艺制备的晶体性能存在较大差异，限制了晶体应用的研究。本项目分别采用富锂熔体生长法和扩散法制备了低掺镁（0.5mol%和1mol%）nSLN晶体，首先对晶体组分和晶体质量进行了表征，高分辨X射线衍射结果表明扩散法制备的低掺镁nSLN晶体结晶质量较好；测试了不同样品的紫外吸收光谱、OH-1吸收谱和拉曼光谱，系统研究了两类晶体晶格缺陷结构，结合制备过程分析了晶格缺陷形成机制。针对中红外QPM-OPO应用对样品非线性系数、激光损伤阈值、畴反转电压等相关性能进行了对比研究，结果表明扩散法制备低掺镁晶体的非线性系数略大、激光破坏性损伤阈值高，富锂熔体法制备晶体光折变损伤阈值高，畴反转电压较低，但畴反转过程中钉扎效应明显，最后分析了晶体缺陷对性能的影响。