名义纯及高掺镁铌酸锂晶体1.06μm激光损伤的研究

Lithium niobate(LiNbO3, LN) crystal is one of few practical electro-optical Q-switching crystals and perfect nonlinear optical crystals, which can be used in BPM-OPO and QPM-OPO pumped by mature 1.06μm laser. LN crystal has important laser applications in many fields, such as laser-measurement, infrared countermeasure, target indication and medical usage. However, the laser-induced-damage(LID) is the most critical factor limiting practical applications. Almost all researches about LID focus on photorefractive effects with short wavelength lasers, and the experimental results of few studies on the infrared wavelength LID are inconsistent or even contradictory. The research status puzzles the practical applications of LN crystals..Aiming at the urgent requirements of many electro-optical fields, this project will systematic study on optical induced damage for the nominally pure LN and highly Mg-doped LN at 1.06μm, explore the mechanism of the photorefractive damage and other LID, and ascertain the influence factors of the damage, then crystals and devices with high LID threshold shall be prepared. As a foundational question of LN crystals being applied in high power infrared laser systems, the LID problem would be resolved through the research work of this project.

作为极少数能够实用的电光调Q晶体和可以采用成熟1.06μm激光泵浦的BPM-OPO或QPM-OPO用非线性晶体，铌酸锂晶体在激光测量、红外对抗、目标指示、医疗等多个领域的激光系统中具有重要应用需求，但激光损伤问题一直是制约其应用的关键。长期以来围绕铌酸锂晶体的激光损伤研究实际上都是以短波长激光的光折变效应为重点，而实际应用的红外激光作用下晶体的激光损伤问题缺乏系统研究，少数研究所报道的结论也不尽一致，数据陈旧甚至互相矛盾，给晶体的实际应用带来巨大困惑。. 本项目面对若干光电领域的迫切需求，针对作为电光和非线性晶体应用的名义纯和高掺镁LN晶体，对其在1.06μm激光典型应用条件下的光折变和非光折变激光损伤问题开展系统工作，研究其光折变性质和非光折变损伤机制，查明影响激光损伤的因素，并初步探索制备高抗激光损伤能力的晶体和器件，以期解决LN晶体在红外强激光系统中应用的基础性问题。

针对若干光电领域的迫切需求，本项目围绕名义纯和高掺镁LN晶体在1.06μm激光典型应用条件下的激光损伤问题开展了系统研究。首先建立了LN晶体缺陷的检测方法及分级标准，对标定组分和缺陷的名义纯及高掺镁LN晶体在实际应用条件的1.06μm激光下进行激光损伤测试，结果表明晶体中缺陷、表面和亚表面的杂质和加工缺陷是影响激光损伤的主要因素，并分析了激光损伤形成的影响机制以及光损伤产生的机理。通过确定最佳原料配比、采用变拉速生长工艺、优化极化和退火工艺等生长了高质量高掺镁LN晶体，晶体直径为三英寸，镁含量均匀性优于0.035mol%/cm。在此基础上，通过改进光学加工工艺控制加工表面麻点、划痕和表面变质层，制备了系列高损伤器件，并对器件的性能进行检测和应用试验，采用高掺镁LN调Q开关获得1.06μm激光的最高输出能量为264mJ。研究成果已经得到国内两家单位的实际应用验证。.在国内外学术刊物上发表论文9篇，培养硕士研究生3名、博士研究生2名，博士后1名。