深紫外非线性光学晶体氟硼酸铯的生长及器件研制

深紫外非线性光学晶体作为产生短波相干光源技术的核心器件，其探索和生长具有重要的研究意义。制备深紫外非线性光学晶体材料关键科学问题在于有效的实现带隙、非线性光学系数、双折射率三个关键性能参数之间的平衡，申请人前期工作提出将[BO3F]4-功能基团引入硼酸盐框架的设计策略，并基于此成功设计合成出CsB4O6F晶体，该晶体继承了唯一能输出深紫外激光的KBBF晶体的优良结构基因，紫外截止边短至155 nm，粉末倍频响应为KBBF的1.2倍，最短相位匹配突破深紫外壁垒，是非常有前景的深紫外非线性光学晶体。但是该晶体生长过程存在组分偏析、熔液粘度大等问题，难以获得高质量单晶。本项目拟通过优化生长工艺，采用顶部籽晶等方法生长晶体，测试热学、线性和非线性光学性质，评估晶体在深紫外全固态激光器的应用前景。该晶体的成功研制，为氟硼酸盐晶体的生长提供技术借鉴，并为中国继续领跑世界深紫外非线性光学领域而添砖助力。

Deep-ultraviolet nonlinear optical (NLO) crystals are of great important as they can generate the deep-ultraviolet coherent light and thus the pursuit of finding novel NLO materials and growing large sizes single crystals has never stopped. The critical point to find practical deep-ultraviolet NLO materials is to achieve the coexistence of three critical parameters (birefringence, NLO coefficients and deep-ultraviolet cutoff edges). In our previous study, we have proposed and verified that [BO3F] is a good unit to balance the multiple criteria among those parameters. Basing on this, CsB4O6F was rationally designed and synthesized, which not only preserves the NLO-favorable structural features of KBBF, but also possesses the optical properties required for the deep-ultraviolet NLO applications, including a short deep-ultraviolet cutoff edge (155 nm), a large SHG response (×1.2 KBBF), as well as deep-ultraviolet shortest SHG phase-matching wavelength (172 nm), suggesting that CsB4O6F is a potential deep-ultraviolet NLO material. But, several challenges including high viscosity and high volatility during the crystal growth process still exist and should be overcome to obtain large-sizes crystals growth with high optical homogeneity. In this project, the crystals of CsB4O6F will be grown by top-seeded solution growth method, and the thermal, linear and nonlinear optical properties of as-grown will be tested. The CsB4O6F-based deep-ultraviolet NLO device will be manufactured to evaluate the potential applications for deep ultraviolet all-solid-state lasers. This project aims at realizing the frequency-doubled deep-ultraviolet laser output, and further accelerating the development of deep-ultraviolet laser source.