大尺寸YCOB晶体包裹体形成机制研究

Ultra-short and ultra-intense lasers have brought brand new experimental methods and extreme physical conditions for scientific research, and have become the leading edge of modern optics. One of the core element in ultra-short and ultra-intense laser system is large size gain materials with high conversion efficiency and high laser-induced damage threshold. YCOB is the most promising gain material for laser application due to their prominent nonlinear-effect and thermo-optic effect, as well as their excellent mechanical property and stability. At present, the main obstacle in YCOB research is the inclusions formed during growth, which will compromise the usable aperture and the laser maximum output power greatly. In this project, we plan to disclose the formation mechanism of inclusions by investigating the types, compositions, forms and their relationships in large size YCOB crystals, and then eliminate inclusions by optimizing the growth composition and velocity, controlling the interface shape, and with successive iteration growth, then finally get the highly homogeneous YCOB crystal components with large size. It is expected to obtain YCOB crystal component with the size of 100 mm×100 mm through the implement of this project, which will be of great meaning to the development of high energy laser technology in our country.

超快超强激光技术为人类提供了前所未有的全新实验手段与极端物理条件，是现代光学领域的重要前沿。其核心器件是大口径、高转换效率以及高抗损伤阈值的稳定增益介质材料。硼酸氧钙钇（YCOB）具有非线性系数及抗损伤阈值高以及机械性能优异的特点，且不潮解、易生长，是超快超强系统中的最佳候选增益材料。目前，YCOB研究的主要问题是，其生长过程中易产生包裹体缺陷，严重影响晶体的可用口径和高功率激光输出。本项目拟通过研究大尺寸晶体中包裹体的类型、成分、形态及其相互关系揭示包裹体形成机制，通过逐次迭代生长，优化晶体生长组分和速度、控制生长界面形状等方法来消除包裹体，从而生长大尺寸高均匀性YCOB晶体，制备大口径晶体元件。本项目有望获得100 mm×100 mm口径的YCOB晶体元件，对大尺寸晶体的生长具有重要的指导意义，对推动我国高能激光的长远发展具有重要的战略意义。

YCOB晶体是一种非常重要的非线性光学晶体材料，具有高非线性系数及抗激光损伤阈值以及优异的机械性能，且不潮解、易生长等优点，是高重频、数拍瓦级激光脉冲系统中二倍频和光参量啁啾脉冲放大过程的最佳候选非线性光学晶体。经过三年来的研究，本项目阐明了三类包裹体缺陷（微观气泡类、宏观气泡类以及纤维状包裹体）的形成机制；探明了YCOB晶体的相分离行为，并首次给出了化学方程式；获得了尺寸为Φ108mm×110mm的无包裹体的高质量YCOB晶体，成功切出了80 mm×60 mm×50mm的YCOB 晶体元件，全口径光学均匀性达到1.7×10-6。晶体元件的尺寸为目前国际上公开报道的最大可用尺寸，达到世界领先水平。本项目的研究成果，将为生长大尺寸、高质量YCOB奠定理论基础，对生长其它大尺寸晶体也具有十分重要的指导意义，对推动我国高能激光的长远发展具有重要的战略意义。