1.6-1.8 μm被动锁模超短脉冲激光在光通信、大气监测、生物医学、国防等领域具有重要应用，但因缺少合适的激光增益介质和非线性可饱和吸收器件，该波段的超短脉冲激光一般难于直接产生。本项目拟针对1.6-1.8 μm特定波段超短脉冲激光的应用需求，结合拓扑绝缘体的宽带非线性可饱和吸收特性，提出拓扑绝缘体可饱和吸收体锁模拉曼光纤激光器的技术路线。与传统稀土离子掺杂类锁模激光器脉冲建立过程不同，拉曼过程的能量转移和激光增益具有瞬时性，本项目将实验研究拓扑绝缘体的宽带可饱和吸收特性，探索拓扑绝缘体超快恢复时间、调制深度等参数对的拉曼光纤激光光源的锁模启动和脉冲建立过程的影响，揭示拓扑绝缘体各宏观参数与拉曼锁模脉冲时域频域特性的内在关系；在此基础上制备参数合适的拓扑绝缘体锁模器件，最终实现1.6-1.8 μm波段稳定、宽调谐的超短锁模脉冲激光输出。

Passively mode-locked ultra-short pulses at 1.6-1.8 μm have attracted considerable attention due to their important applications in areas such as telecommunications, atmosphere monitoring, biomedicine and national defense. However, ultra-short pulsed lasers operating at this wavelength range are generally not available owing to the lack of appropriate laser gain medium and nonlinear saturable absorption mode-locking components. In this application, an effective lasing scheme is proposed for the requirement of ultra-short pulsed laser sources at this special wavelength range of 1.6-1.8 μm, by using a new ultra-broad nonlinear saturable absorber of topological insulator (TI) as the mode-locker in wavelength-flexible Raman fiber lasers. Different to traditional rare-earth-ion-doped mode-locked lasers with typical energy storage process, the SRS process in Raman fiber laser counterparts is characteristic of its immediate gain response and fast energy transfer. The broadband nonlinear optical properties of TIs will be investigated in this application. In addition, the mode-locked pulse building-up process in Raman fiber lasers is experimentally investigated including the impact of TIs’ specific parameters such as recovery time and modulation depth. The intrinsic relationship between the characteristics of the TIs and the time-frequency properties of ultrafast pulses will also be studied. Based on the qualified TI saturable absorber with appropriate parameters, potential to obtain a stable, broadly tunable laser emission in the particular wavelength range of 1.6-1.8 μm will be explored experimentally.