二硫化钼/钨薄膜的非线性光学特性及器件应用研究

Molybdenum/tungsten disulfide (Mo/WS2) films that exhibit ultra-high photoluminescence efficiency and nonlinear coefficient are two-dimensional semiconductor materials with a non-zero bandgap. They have wide application prospects in fields of digital circuits and optoelectronics, and thus become one of the most interesting research topics in the worldwide range. The main propose of this project is to reveal the behavior and formation mechanism of nonlinear interaction between Mo/WS2 films and ultrafast lasers, realize film-based photonic devices, and develop its applications in the areas of wavelength conversion and ultrafast optics. To achieve these, the following studies will be carried out: (1) Optimize the preparation method of films, obtain physical parameter controllable film samples, as well as investigate the influence of layers and defects on the optical absorption property and band structure; (2) Study the second- and third-order nonlinear optical response characteristics of films, propose a physical model to describe the interaction between films and ultrafast lasers; analyze formation mechanisms of four-wave-mixing, high-order harmonics generation, and broadband saturable absorption in films; (3) Develop wavelength converter and saturable absorber by utilizing the nonlinear property of films and combining the polymer planar waveguides as well as microstructure fibers. The obtained results not only help to get a new understanding of optical nonlinearity about Mo/WS2 films, but also provide theoretical basis and necessary photonic devices for optical communications and ultrafast lasers.

二硫化钼/钨（Mo/WS2）薄膜是具有带隙的二维半导体材料，它们具有极高的光致发光效率和非线性系数，在数字电路和光电子学等领域具有广阔的应用前景，成为了世界范围内的研究热点之一。本项目旨在揭示Mo/WS2薄膜中非线性光学效应的作用方式和形成机制，实现基于此类薄膜的光子器件，并发展其在波长转换、超快光学方面的应用。拟开展以下方面研究：①优化薄膜的制备方法，获得物理参数可控的薄膜样品；探讨原子层数、缺陷对薄膜光学吸收特性和能带结构的影响；②研究薄膜二阶、三阶非线性光学响应的特点，提出薄膜与超快激光相互作用的物理模型；分析薄膜中四波混频、高次谐波产生、宽带可饱和吸收等效应的形成机制；③利用薄膜的非线性光学特性，结合聚合物平面光波导、微结构光纤开发波长转换器和可饱和吸收体。相关研究成果将有助于人们对Mo/WS2薄膜非线性特性获得新认识，并且可以为光通信和超快激光等领域提供理论基础和必要的光子器件。

过渡金属硫化物是具有带隙的二维半导体材料，它们具有极高的光致发光效率和非线性系数，在数字电路和光电子学等领域具有广阔的应用前景，成为了世界范围内的研究热点之一。本项目旨在揭示过渡金属硫化物与激光非线性相互作用的机制，实现基于此类材料的可饱和吸收器件，并发展其在锁模、调Q光纤激光方面的应用。项目开展的主要研究内容包括：①利用液相剥离法制备了少层过渡金属硫化物纳米片（包括MoS2、WS2、ReS2、MoSe2、WSe2、MoTe2、WTe2），表征了所得纳米片的尺寸、厚度及拉曼光谱特性，研究了材料吸收系数与波长的关系；②基于第一性原理，研究了少层WS2中原子比例对能带结构的影响，发现W或S原子缺陷均会降低材料的带隙。由于S原子量较小，其与强脉冲相互作用时比W更易被替换，而且实验观测到的缺陷主要是S缺陷，表明S缺陷对WS2的宽带可饱和吸收起决定作用；③将所得过渡金属硫化物纳米片与D形光纤或聚合物薄膜结合，获得了两类低成本、高损伤阈值的可饱和吸收体，在光纤激光器中实现了单孤子、多孤子以及谐波孤子锁模；④对比了过渡金属硫化物和其他低维纳米材料（如黑磷、碳纳米管和铁氧化物）可饱和吸收特性的异同，并在矢量光场/涡旋光场光纤激光器方面开展了一定的拓展性研究。该项目培养研究生4名，共发表SCI论文19篇，其中影响因子大于3的论文14篇，被SCI引用400余次。3篇论文入选ESI“高被引论文”，1篇论文入选“热点论文”。