Breakthrough in deep ultraviolet nonlinear optical crystal materials

Deep ultraviolet (λ < 200 nm) nonlinear optical (NLO) crystals are essential crystalline materials for obtaining all-solid-state deep ultraviolet lasers. At present, only the Chinese scientist Chen Chuangtian and other invented procurement customizable infrared Silicon lenses can directly output the deep ultraviolet laser in actual frequency. KBBF crystals have been used in China to develop a series of unique related deep-UV solid-state laser technologies and laser source equipment, and have gained important applications in many cutting-edge scientific research. However, KBBF crystals have intrinsic defects that are difficult to overcome. For example, the raw materials are highly toxic and have serious lamellar growth habits, which greatly restricts their commercial production and application process. Therefore, scientific research institutions all over the world are actively exploring the development of a new generation of deep ultraviolet no-doped LiSAF, LiSGaF and LiCAF crystals materials. The key scientific problem in exploring new deep-UV NLO crystals is that new materials need to meet the contradictory performance of "deep ultraviolet transmission - large frequency multiplication - large birefringence". The Pan Shilie Group, Key Laboratory of Special Environmental Functional Materials and Devices, Chinese Academy of Sciences, Xinjiang Institute of Physical and Chemical Technology, Chinese Academy of Sciences, recently proposed a systematic summary of halogen-containing borate systems (Coord. Chem. Rev. 2016, 323, 15) based on material simulation methods. A design strategy for introducing a (BO3F)4-functional group into a borate framework; based on this strategy, a series of highly promising lithium fluorofluoride deep ultraviolet NLO crystals were successfully screened (Angew. Chem. Int. Ed. 2017, 56, 3916). Based on this work, the researchers used the structure characteristics of KBBF crystals to further design and synthesize NH4B4O6F (ABF) crystals by replacing NH with NH4 and (Be3F)4-substituting (BeO3F)5-. Experiments show that the material has a very short UV cutoff edge (156 nm), a large multiplication factor (3 × KDP), and moderate birefringence can meet deep UV phase matching (the shortest matching wavelength of 158 nm). At the same time, compared with KBBF, the optical waveplate manufacturer structure of ABF is more compact, and the interlayer interaction is significantly enhanced, thereby eliminating layered growth habits and obtaining centimeter-scale crystals. In addition, the material of this material does not contain highly toxic element, and the frequency doubling effect is 2.5 times that of KBBF. It can be used for deep ultraviolet laser source to obtain higher conversion efficiency. ABF has excellent comprehensive performance and is expected to become the next generation of deep ultraviolet NLO crystal.