以非线性光学晶体为核心的355nm紫外激光，在精密微加工、医疗、光通讯、光刻、军事等领域具有重大的应用价值。KBB（K3B6O10Br）晶体具有大的非线性光学系数（d22=1.23pm/v),短的紫外截止波长（182nm),不潮解、易于加工等性能。在我们前期的研究基础上，找到了新的助熔剂体系(氧化物-氟化物)并生长了单晶，实现了45.5W的高功率倍频激光输出（发表在Opt.Lett,40(2015)1073)。本项目主要研究大尺寸的KBB助熔剂体系优化和单晶生长，解决200-280nm紫外波段非本征吸收的问题，研究晶体器件的三倍频参数（包括有效倍频系数,匹配角,接受角,温度带宽,走离角等),以及首次实现三倍频355nm的瓦级输出,并最终评估其在紫外波段应用前景。作为潜在有应用前景的三倍频晶体，KBB晶体的深入研究对继续保持我国在紫外非线光学晶体领域领先地位具有一定意义。

Ultraviolet (UV) lasers at 355 nm through frequency conversion technique by core materials of nonlinear optical (NLO) crystals have been widely used in the fields of fine manufacturing, medicine, optical communication, optical lithograph, military, etc. KBB (K3B6O10Br) NLO crystal possesses large NLO coefficient (d22=1.23 pm/v), short UV cut-off (182 nm), nondeliquescence and good mechanical properties. In our previous studies, KBB crystals were successfully grown from the metal oxide-fluoride flux system. And using KBB crystal, a 45.5 W nanosecond 532 nm average power output was obtained via second harmonic generation (Published in Opt. Lett, 40(2015)1073). In this project, we will mainly investigate optimization of flux system, crystal growth with larger sizes, solution of UV absorption in the range of 200-280 nm, third harmonic generation (THG) optical parameters (including effective NLO coefficient, acceptance, temperature and walk-off angles) and achievement of THG watt level power output for the first time. KBB crystal is a new promising NLO crystal application in the field of THG process. Thus, as a new potential NLO crystal, the research for the bulk crystal growth and THG properties of KBB crystal is also very important to generate UV laser at 355 nm.