新型深紫外非线性光学晶体γ-Be2BO3F生长和性能研究

Deep-ultraviolet （DUV, <200nm）all solid state laser plays an important role in high-resolution cutting-edge scientific equipment and laser technology and so on. KBe2BO3F2 (KBBF) is currently the only practical DUV nonlinear optical (NLO) crystal, which can realize the DUV laser output by direct frequency doubling. However, the serious layered habit makes it difficult to grow thick, which limits its application. In the preresearch, the applicant designed and synthesized a new DUV NLO crystal γ-Be2BO3F (γ-BBF)，which effectively overcomes the layered habit and possesses a short UV cutoff edge of 145 nm. By theoretical prediction, the shortest phase matching wavelength can reach 146 nm, which means that the performance of the crystal is expected to significantly exceed KBBF. At present, there are difficulties in crystal growth, and there is still a certain distance from practical application. This project intends to study the phase transition mechanism and relationship of crystals as well as related phase diagram, find the suitable flux, and then explore the growth technology of millimeter-sized γ-BBF crystal by the atmospheric pressure and sealed molten-salt growth method. Among them, the phase change and interaction mechanism of raw materials under sealed conditions and technical optimization of this method will be study. In addition, the basic optical and physical properties will be characterized and evaluated. These studies will lay the foundation for application of γ-BBF in DUV frequency conversion.

200nm以下深紫外全固态激光在高分辨率前沿科学设备和激光科技等领域具有重要应用。KBe2BO3F2（KBBF）是目前唯一实用的能通过直接倍频实现深紫外激光输出的非线性光学晶体。由于其严重的层状习性使晶体很难长厚，而限制了其应用。申请人在预研中设计合成一例新型深紫外非线性光学晶体γ-Be2BO3F（γ-BBF）。该晶体有效克服了层状习性，紫外透过截止边可达145nm，理论预测相位匹配范围可达146nm，性能有望大幅超过KBBF。目前晶体生长存在困难，离实用化还有一定距离。本项目拟从晶体的相变机理和相关系以及相规律研究入手，寻找合适的助熔剂，通过常压熔盐和密封熔盐两种方法研究晶体生长技术，其中包括密封条件下物相变化和相互作用机理的研究及这一新方法的技术性探索，以实现数毫米级晶体生长技术的突破。此外，对晶体基本光学及物化性能进行表征与评估，为晶体深紫外的变频应用奠定基础。

KBe2BO3F2（KBBF）是目前唯一实用的深紫外非线性光学晶体。但是严重的层状习性使晶体很难长厚，从而限制了其应用。我们发现的新型深紫外非线性光学晶体γ-Be2BO3F（γ-BBF）在结构上有效克服了层状习性，其理论紫外透过截止边可达145nm，最短相位匹配波长可达146nm。该晶体存在多种不利相变，而我们所需的晶相极难生长。本项目以γ-BBF晶体的生长和性能研究为主要出发点，从相变研究、多晶料合成、助熔剂和矿化剂的寻找展开了研究。我们从传统敞开系统固相熔盐法到密封熔盐法再到水热法都进行了大量的试验，系统地开展了有效助熔剂和矿化剂的寻找，但是尚未寻找到生长足够尺寸晶体的助熔剂和矿化剂用于进一步开展性能探索。不过我们在项目执行过程中积累了较多有价值的经验，这或将为进一步的晶体生长研究提供重要的线索。在项目执行过程中发现的数例具有类KBBF结构的新型非线性光学晶体也将对该类化合物体系甚至深紫外晶体的研究具有重要的意义。此外，基于相关晶体生长研究的经验和对结构-性能关系的了解，我们还成功开发了几例高性能的有潜在应用价值的非线性光学晶体材料。项目相关研究成果发表在J. Am. Chem. Soc.（1篇）、Angew. Chem. Int. Ed.（2篇）、Chem. Mater.（2篇）、Chem. Sci.（1篇）和Cryst. Growth Des.（1篇）等国际知名学术期刊上发表SCI论文7篇；申请中国专利3项，其中2项已获得授权。协助培养硕士研究生1人，博士研究生1人。