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Nonlinear Optical Mechanism of β-BaB2O4 Revealed by Experimental Electron Density
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2023-09-28 , DOI: 10.1002/adom.202301897
Long‐Qi Yang 1, 2 , Xiao‐Ming Jiang 1 , Yu Chen 1 , Bin‐Wen Liu 1 , Guo‐Cong Guo 1, 2
Affiliation  

Nonlinear optical (NLO) materials are of immense scientific and technological importance. However, debate has long prevailed theoretically regarding the structural origin of the second harmonic generation (SHG) effect. In this work, the experimental electron density (ED) of controversial β-BaB2O4 (BBO) is studied by high-resolution X-ray diffraction, indicating that the [B3O6]3− motif dominates two large non-zero SHG tensors (d222 and d311) while Ba atoms contribute mostly to the smallest one (d333), and the atomic SHG contributions of terminal O atoms in [B3O6]3− motifs are much larger than those of B and bridged O atoms, clarifying the disputes on its NLO response mechanism. Besides, the contraction of inner electron shells (5s25p6) of the Ba atom and partial covalent behavior of the Ba─O interaction are first observed experimentally. Furthermore, the SHG coefficients of BBO derived from experimental ED are in excellent agreement with those from bulk crystals, providing a high-efficient and low-cost method of screening high-performance NLO materials with just an easy-to-obtain tiny crystal.

中文翻译:

实验电子密度揭示β-BaB2O4的非线性光学机理

非线性光学(NLO)材料具有巨大的科学和技术重要性。然而,关于二次谐波产生(SHG)效应的结构起源,理论上长期以来一直存在争论。在这项工作中,通过高分辨率X射线衍射研究了有争议的β -BaB 2 O 4 (BBO)的实验电子密度(ED) ,表明[B 3 O 6 ] 3−基序主导了两个大的非-基序。零倍频张量(d 222d 311),而 Ba 原子主要贡献最小的张量(d 333 ),并且 [B 3 O 6 ] 3−基序中末端 O 原子的原子倍频贡献远大于 B并桥接O原子,澄清了其NLO响应机制的争议。此外,Ba原子内电子层(5 s 2 5 p 6 )的收缩和Ba─O相互作用的部分共价行为也是首次在实验上观察到。此外,实验ED得到的BBO的SHG系数与块状晶体的SHG系数非常吻合,为仅用易于获得的微小晶体筛选高性能NLO材料提供了一种高效、低成本的方法。
更新日期:2023-09-28
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