Yb,Mg双掺近化学计量比钽酸锂晶体缺陷的形成与抑制机理及高品质晶体的生长

Near-stoichiometric Yb,Mg:LiTaO3 crystal is a good candidate for laser performance. Combined with the advantages of preparing periodic structure, it realizes the self-frequency-tuning laser output with its high non-linear optical property, and has become an important foundational material for green laser and infrared laser performance. Since plenty of defect structures are easily formed during the growth, such as the antisite defects, the imhomogeneous dopants distribution, it is very difficult for the growth of near-stoichiometric LiTaO3 with high quality. Therefore, in the proposal, the modern techniques such as the neutron diffraction and the usage of isotope will be applied to discuss the formation and inhibition mechanism of the antisite defects. The mechanism for the control of the defect structures by the elemental doping and the crystal growth technique will be confirmed. Then, the synthesis of high homogeneous doped LiTaO3 multicrystalline powders by the partial wet route and spray drying method will be well discussed. On basis of the independent intelligent property right on the hanging double crucible and the self-feeding system, the Yb,Mg double-doped near-stoichiometric LiTaO3 crystal will be obtained. The electronic field periodically poled of the high quality crystal as well as the laser performance will be performed. This study will provides an understanding of the formation of intrinsic defects in theory, as well as the experimental basis. It also provides a common reference for the crystal growth technology. The as-obtained materials provide material support for the development of the laser display technology and other fields.

Yb,Mg双掺近化学计量比钽酸锂晶体与周期性极化技术相结合，可以同时实现激光和倍频或者光参量振荡的功能，进而实现自倍频或者自OPO激光输出，将成为下一代小型高效绿色激光和红外激光的关键材料。然而由于钽酸锂晶体生长过程中易形成反位缺陷、掺杂元素分布不均匀等微观结构缺陷，使得高品质晶体的生长非常困难。本研究拟利用包括中子衍射和同位素使用等多种现代研究手段，结合理论模拟，研究晶体中反位缺陷的成因和抑制机理，明确元素掺杂、生长工艺对晶体微观缺陷结构的抑制机理，在此基础上通过研究半液相法-喷雾干燥合成技术，实现均匀掺杂钽酸锂多晶料的合成，利用具有自主知识产权的悬挂坩埚-自动加料晶体生长设备，生长高质量的双掺近化学计量比钽酸锂晶体，并对晶体进行周期极化实验和激光性能表征。本研究为理解此类晶体本征缺陷的形成提供理论和实验依据，为晶体生长的共性技术研究提供参考，为激光显示技术等领域的发展提供基础材料支撑。

在激光显示、激光雷达、和光电对抗等领域对固态激光的有着不同的需求，激光频率调谐是其关键的技术，此技术基于非线性光学晶体的相位匹配，受到了晶体本征特性的限制。准相位匹配(QPM)变频技能够更好的利用晶体非线性系数，而具有反向畴结构，便于实现周期性晶格结构调控的光学晶体，如铌酸锂、钽酸锂晶体成为非线性光学研究中的重要基础材料。由于此类晶体本征非化学计量比特性，获得的晶体中反位缺陷会对光学性能产生显著影响，掺杂和近化学计量比晶体生长是消除缺陷影响的重要途径。此外，为了实现激光器件的集成化，自倍频技术等需要材料进行激活离子掺杂。因此，本项目主要开展了：1. 反位缺陷的抑制方法和原理研究，明确了通过均匀Mg离子掺杂，可以抑制Nb-Li反位缺陷的形成，进而提高材料光学性质，说明了掺杂离子均匀性的重要性；2. 晶体中镁离子的均匀性研究及改进型半液相法均匀元素掺杂多晶料的制备工艺，进一步说明了非均匀掺杂造成的掺杂物质的状态为聚集体，提出的改进型均匀掺杂多晶料制备工艺能够解决多晶料批量制备的困难；3. MgO:CLN，MgO:SLN和LT晶体生长技术的数值模拟研究，完善了多种晶体生长模拟技术，成功对晶体生长过程进行了指导，此方法的推广可以大幅降低晶体生长参数探索周期；4. MgO:SLN晶体，Nd、Mg双掺SLN晶体，Nd、Mg双掺LT晶体的生长，获得了良好质量的晶体，证明晶体生长基本工艺的合理性；5. 基于电场极化制备的周期极化铌酸锂晶片的激光性能研究，明确了周期计划过程中畴结构调控机制，实现了多种周期的PPLN晶体制备，并利用稀土掺杂的PPLN晶体首次实现了自倍频绿光输出；6. Yb、Er双掺化学计量比铌酸锂晶体的生长和性质研究，首次实现了双稀土离子掺杂的近化学计量比晶体的生长，并发现低缺陷浓度有利于其光谱性质的体现。