Xu Jingjing, Wu Kui, Xiao Yan, Zhang Bingbing, Yu Haohai, Zhang Huaijin
College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China.
State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan 250100, China.
ACS Appl Mater Interfaces. 2022 Aug 24;14(33):37967-37974. doi: 10.1021/acsami.2c11199. Epub 2022 Aug 11.
Nonlinear optical (NLO) crystals are of importance on extending infrared (IR) laser wavelengths. Considering their performance drawbacks in commercial IR NLO crystals, a recent challenge in exploring new excellent IR NLO crystals is how to break the inherent conflict between a wide bandgap ( ≥ 3.0 eV) and large NLO effect ( ≥ 0.5 × AgGaS) and simultaneously enlarge the birefringence (Δ) for a requisite phase-matching (PM) behavior. For that reason, rational combination of mixed-anion functional groups into a crystal structure affords the successful design and synthesis of six LnMGaSO (Ln = La, Pr, and Nd; M = Ca and Sr) NLO oxysulfides. Among them, LaMGaSO satisfy the property-balance demand (: 3.21-3.27 eV and : 0.9-1.0 × AgGaS) as promising PM NLO crystals through gathering their property advantages between LaMGaO and LaMGaS by mixed-anion-oriented performance engineering. A study on the structure-property relationship indicates that heteroleptic (Ln/M)SO and GaSO anionic groups are proven as promising NLO-active units and offer a great synergistic effect on the NLO origin. This work as a visualized model not only provides a first clear cognition on varying properties from oxide to sulfide to oxysulfide but also highlights the feasibility of mixed-anion-oriented design of new NLO candidates with balanced performances.
非线性光学（NLO）晶体对于扩展红外（IR）激光波长具有重要意义。考虑到商业红外非线性光学晶体的性能缺陷，探索新型优质红外非线性光学晶体的一个最新挑战是如何打破宽带隙（≥3.0 eV）和大非线性光学效应（≥0.5×AgGaS₂）之间的固有矛盾，同时增大双折射（Δ）以实现必要的相位匹配（PM）行为。因此，将混合阴离子官能团合理组合到晶体结构中，成功设计并合成了六种LnMGaSO₄（Ln = La、Pr和Nd；M = Ca和Sr）非线性光学硫氧化物。其中，LaMGaSO₄通过混合阴离子导向的性能工程，聚集了LaMGaO₄和LaMGaS₂之间的性能优势，满足了作为有前景的相位匹配非线性光学晶体的性能平衡要求（Eg：3.21 - 3.27 eV和d₃₆：0.9 - 1.0×AgGaS₂）。结构 - 性能关系研究表明，杂配（Ln/M）SO₄⁻和GaSO₄³⁻阴离子基团被证明是有前景的非线性光学活性单元，并对非线性光学起源产生了巨大的协同效应。这项工作作为一个可视化模型，不仅首次清晰地认识了从氧化物到硫化物再到硫氧化物的性能变化，还突出了混合阴离子导向设计具有平衡性能的新型非线性光学候选材料的可行性。
