基于二维MoS2/Graphene异质结饱和吸收的超快激光研究

The molybdenum disulfide (MoS2), a novel 2D crystals after graphene, have recently attracted much attention due to their excellent opto-electronic properties and potential applications in optoelectronics. However, few-layer MoS2 has extremely disadvantages with poor thermal property and low optical damage threshold, which would strongly limit its applications in ultrafast mode-locked solid-state lasers. In this project, we plan to employ the method of liquid phase-based exfoliation and intercalation to develop multistacked composite by combining MoS2 with graphene in heterostructure. The damage threshold and stability of the formed novel hybrid MoS2/Graphene (MoS2/G) composite are expected to be improved. Focusing on the single- or multi-layer MoS2/G nanophase composite, we will investigate its nonlinear saturable absorption based passive mode-locking dynamics in details and reveal the relationship between the MoS2/G composite properties and ultrafast pulse generation, operation stability and self-start ability in the satruable absorber (SA) mode-locking process. Exploiting the broadband saturable absorption properties of the MoS2/G nonlinear SA in the solid-state mode-locked laser based on the broadband gain medium Yb:CALGO crystal, femtosecond pulses are expected to be generated. The research results will illustrate the potential of 2D-MoS2/G composite to be used in the photo-electronic devices and give more comprehension on such compound function material for both foundational research and practical applications.

层状二硫化钼(MoS2)是继石墨烯之后又一新型二维光电功能材料，因其具有优秀的光电特性和应用前景，受到人们强烈关注。但MoS2由于自身存在抗光伤和热传导性能较差等缺陷，使其在超快锁模固体激光器件中的应用受到限制。本项目利用液相剥离插层方法，将MoS2与同类二维材料石墨烯复合，形成新型MoS2/Graphene(MoS2/G)异质结构，以提高其抗光伤能力和稳定性。项目将以单层或数层MoS2/G为研究对象，开展二维MoS2/G非线性饱和吸收被动锁模动力学过程的研究；深入探讨锁模超快脉冲的生成、稳定及自启动过程与饱和吸收特性参量之间的内在关系；将MoS2/G应用在宽带增益介质Yb:CALGO激光器中，实现基于MoS2/G饱和吸收的飞秒激光输出。项目的研究对深入了解MoS2/G这种二维异质结材料在固体超快光电子器件中的应用有重要的应用价值和科学意义。

由不同种类的二维材料堆叠而成的范德华力异质结材料可以组装成多种新型材料，因其具有许多新奇的物理性质而受到人们强烈关注。本项目中，我们从波长敏感性、不同的堆叠方式、层数三个方面系统地研究了石墨烯/二硫化钼异质结（G/MoS2）的非线性光学响应特性。通过将不同层数的MoS2与单层的Graphene复合，使异质结的层间耦合作用得到了调节，并起到了界面增强的效果。利用开孔Z扫描技术和泵浦探测技术，对G/MoS2异质结的饱和吸收作用和暂态吸收动力学过程进行测试。基于第一性原理，计算了不同层数的G/MoS2的功函数变化情况，并对材料内部电荷转移过程进行分析，详细探讨了锁模激光器性能与饱和吸收特性参量之间的内在关系。将不同层数的异质结样品作为光调制元件，实现了调Q脉冲输出，并对激光器性能进行对比分析。实验结果与理论计算结果完全一致。利用G/MoS2异质结超快的饱和恢复时间和强烈的饱和吸收作用，在1微米近红外波段成功实现飞秒和皮秒固态激光器。以Nd:YVO4, Yb:KYW, Yb:CALGO激光晶体作为增益介质，分别实现了脉冲宽度16.83 ps, 236 fs, and 92 fs的锁模脉冲输出，相应的重复频率为0.94 GHz, 41.84 MHz, and 84.5 MHz。另外，我们还用液相剥离法制备了氧化石墨烯与二硫化钼的异质结样品，并且实现了调Q和锁模运转，其脉冲宽度分别为48.7 ns和17.15 ps。项目研究结果对二维材料的可控堆叠以及异质结材料在固体超快光电器件中的应用有重要的应用价值和科学意义和科学意义。