采用化学气相沉积法制备了直立生长的SnS₂（V-SnS₂）薄膜，并使用自主搭建的Z扫描系统研究了V-SnS₂的三阶非线性光学响应。结果表明，由于S空位的存在使得V-SnS₂薄膜表现出明显的饱和吸收响应，且非线性吸收系数（β）随着泵浦功率的增加而减少。分析发现，其β的最大值为6 cm/GW，调制深度（ΔM）为50%。同时，通过闭口Z扫描技术测量发现V-SnS₂薄膜的n₂比Si和GaAs大一个数量级，且n₂随着泵浦功率的增加而减少，基于自由载流子的非线性理论分析表明这与材料中的自由载流子和束缚电子密切相关。本文研究证明V-SnS₂在全光开关、激光调Q等非线性光电子器件的设计与制造方面有潜在的应用。

通过太赫兹发射光谱研究了400 nm飞秒激光脉冲激发层状MoSe₂所引起的物理效应。太赫兹振幅随泵浦功率、方位角、偏振角的依赖关系表明，太赫兹辐射主要由表面耗尽场诱导的光生电流和二阶非线性极化诱导的移位电流这两种瞬态光电流效应共同引起，并且两种电流的贡献分别为82%和18%。研究结果可为MoSe₂在超快光学领域的发展和应用提供实验支持。

Understanding and controlling defect in two-dimensional materials is important for both linear and nonlinear optoelectronic devices, especially in terms of tuning nonlinear optical absorption. Taking advantage of an atomic defect formed easily by smaller size, molybdenum disulfide nanosheet is prepared successfully with a different size by gradient centrifugation. Interestingly, size-dependent sulfur vacancies are observed by high-resolution X-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy. The defect effect on nonlinear absorption is investigated by Z-scan measurement at the wavelength of 800 nm. The results suggest the transition from saturable absorption to reverse saturable absorption can be observed in both dispersions and films. First principle calculations suggest that sulfur vacancies act as the trap state to capture the excited electrons. Moreover, an energy-level model with the trap state is put forward to explain the role of the sulfur vacancy defect in nonlinear optical absorption. The results suggest that saturable absorption and reverse saturable absorption originate from the competition between the excited, defect state and ground state absorption. Our finding provides a way to tune the nonlinear optical performance of optoelectronic devices by defect engineering.

The plasmonic mode in graphene metamaterial provides a new approach to manipulate terahertz (THz) waves. Graphene-based split ring resonator (SRR) metamaterial is proposed with the capacity for modulating transmitted THz waves under normal and oblique incidence. Here, we theoretically demonstrate that the resonant strength of the dipolar mode can be significantly enhanced by enlarging the arm-width of the SRR and by stacking graphene layers. The principal mechanism of light–matter interaction in graphene metamaterial provides a dynamical modulation based on the controllable graphene Fermi level. This graphene-based design paves the way for a myriad of important THz applications, such as optical modulators, absorbers, polarizers, etc.