在被动锁模光纤激光器中，可饱和吸收体是实现其锁模的核心器件，改良其性能是获得高性能脉冲激光稳定输出的突破口。传统的半导体可饱和吸收镜存在制备工艺复杂、成本高、吸收带宽窄等问题，因此急需开发工艺简单、成本低、工作波长范围宽的新型高性能可饱和吸收体材料。量子点由于其较低的非饱和损耗、大的非线性吸收系数和调制深度成为极具潜力的可饱和吸收体材料，然而，其易团聚和氧化而限制了在非线性光学方面的应用。本项目拟采用浸渍提拉法设计制备出量子点/石墨烯异质结可饱和吸收体，利用石墨烯优异的热稳定性和化学稳定性来克服量子点易团聚和氧化的问题，同时结合石墨烯宽波段响应和激子恢复时间短的光学优势形成互补效应，获得高功率短脉宽长时间稳定输出的高性能可饱和吸收体。并进一步将其应用于近红外锁模光纤激光系统，研制基于该新型异质结可饱和吸收体的具有稳定输出的超快光纤激光系统，推动新型锁模激光器的发展。

In a passively mode-locked fiber laser, a saturable absorber is the core device that achieves its mode-locked operation and improving its quality is the breakthrough to obtain stable and high-performance laser. Currently, the traditional semiconducting saturable absorber mirrors have problems such as complex preparation methods, high cost and narrow working wavelength range. So, it is necessary to explore novel saturable absorption materials with advantages such as simple preparation method, low cost and broad working wavelengh range. Quantum dots have been potential candidates owing to their low unsaturated loss, large nonlinear absorption coefficient and modulation depth. However, it is easy to aggregate and being oxidized that limites its nonlinear optical application. In this project, quantum dot / graphene heterojunction saturable absorber are fabricated through simple dip coating method. The excellent thermal and chemical stability of graphene can protect the optical property of quantum dots. Meanwhile, combining the advantages of broad wavelength response, short exciton recovering time of graphene and the unique optical property of quantum dots, in order to obtain stable high quality saturable absorbers. The novel heterostructure saturable absorber will finally be used in a near-infrared mode-locked fiber laser system to form picosecond and femtosecond ultrafast fiber laser with stable output, promoting development of the novel mode-locked lasers.