vdWs 铁电 NbOI2 中二次谐波产生的发射偶极子和压力驱动可调谐性,Advanced Functional Materials

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vdWs 铁电 NbOI2 中二次谐波产生的发射偶极子和压力驱动可调谐性
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2023-10-05 , DOI: 10.1002/adfm.202308207
Jierui Fu ₁ , Niuzhuang Yang ₂ , Yue Liu ₁ , Quan Liu ₃ , Jiaxin Du ₄ , Yuqiang Fang ₅ , Jiapeng Wang ₁ , Bo Gao ₄ , Chengyan Xu ₆ , Dai Zhang ₃ , Alfred J. Meixner ₃ , Gaoyang Gou ₇ , Fuqiang Huang ₅ , Liang Zhen ₆ , Yang Li ₁

Affiliation

二维面内铁电NbOI ₂表现出强大的二次谐波产生（SHG）和超高的有效磁化率。为了推动它们在非线性光子学和光电子学中的应用，非常需要了解二次谐波的发射偶极子方向和可调谐性，但目前尚未实现。在这里，通过将抛物面镜的紧密聚焦与后焦平面（BFP）成像技术相结合，首次证明了NbOI ₂的SHG发射呈现与数值模拟一致的纯面内偶极子方向，这表明面内NbOI ₂中的二次谐波磁化率张量的分量主导了发射。此外，借助从头计算，发现静水压力可以显着改变NbOI ₂的结构和由此产生的SHG强度。明确地说，SHG强度由于低压下八面体的变形而略有增加，然后由于结构对称性的改善而随着压力的进一步增加而单调下降，以及铁电到顺电相变导致的急剧淬灭。这项工作明确地证明了倍频的偶极子发射行为以及结构演化与倍频强度之间的关系，为可调谐非线性光学和光电子学提供了途径。

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Emission Dipole and Pressure-Driven Tunability of Second Harmonic Generation in vdWs Ferroelectric NbOI2

2D in-plane ferroelectric NbOI₂ exhibits strong second harmonic generation (SHG) and ultrahigh effective susceptibility. To push forward their applications in nonlinear photonics and optoelectronics, it is highly desirable to understand the emission dipole orientation and tunability of SHG, which is not achieved. Here, by integrating tight focusing from parabolic mirror with back focal plane (BFP) imaging technique, for the first time it is demonstrated that SHG emission of NbOI₂ presents purely in-plane dipole orientation in consistent with numerical simulations, suggesting the in-plane components of the SHG susceptibility tensor in NbOI₂ dominate the emission. Moreover, with the aid of ab-initio calculations, it is found that the hydrostatic pressure can dramatically change the structure and resultant SHG intensity of NbOI₂. Explicitly, SHG intensity endures a slight increase due to the distortion of octahedral at low pressure pressure, and then monotonously decreases due to the improvement of structural symmetry with further increasing pressure, and drastically quenching resulting from the ferroelectric to paraelectric phase transition. This work unambiguously demonstrates the dipole emission behavior of SHG and the relationship between structural evolution and SHG intensity, which provides an avenue for tunable nonlinear optics and optoelectronics.

更新日期：2023-10-05

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