Yang Guang, Yu Lianmeng, Fu Zhaoming, Yang Peizhi, Feng Xiaobo
Opt Express. 2025 Feb 24;33(4):7862-7872. doi: 10.1364/OE.539504.
We report our theoretical investigation into both the twist angle-dependent and the electric field-controlled second harmonic generation (SHG) effect in twisted bilayer graphene (tBLG) based on the four-band continuum model and independent-particle approximation. This analytical theory provides a quantitative explanation for the twist angle-dependent SHG effect observed in noncentrosymmetric tBLG, as reported in [Matter3, 1361 (2020)10.1016/j.matt.2020.08.018], which represents a groundbreaking exploration introducing the twisting degree of freedom into nonlinear optics. Due to the one-photon and two-photon resonant transitions as well as the strong interlayer coupling, the SHG susceptibility of tBLG, which primarily stemmed from interband transitions, can reach up to 10 pm/V and increases as the twist angle decreases. Additionally, the application of an external electric field can boost the SHG susceptibility by at least one order of magnitude and effectively tune both the magnitude and the positions of the absorption peak with wider range by manipulating the movement of Dirac cones and van Hove singularities. These findings provide valuable insights for the design and implementation of optoelectronic devices with wide-band tunability and high-performance.
我们基于四能带连续模型和独立粒子近似，报告了对扭曲双层石墨烯（tBLG）中与扭曲角相关以及电场控制的二次谐波产生（SHG）效应的理论研究。如[Matter3, 1361 (2020)10.1016/j.matt.2020.08.018]所报道，该分析理论为在非中心对称tBLG中观察到的与扭曲角相关的SHG效应提供了定量解释，这代表了将扭曲自由度引入非线性光学的开创性探索。由于单光子和双光子共振跃迁以及强层间耦合，主要源于带间跃迁的tBLG的SHG极化率可达10 pm/V，并随着扭曲角减小而增加。此外，施加外部电场可将SHG极化率提高至少一个数量级，并通过操纵狄拉克锥和范霍夫奇点的移动，在更宽范围内有效地调节吸收峰的幅度和位置。这些发现为具有宽带可调性和高性能的光电器件的设计与实现提供了有价值的见解。
