基于拓扑绝缘体锁模的可调谐多波长飞秒光纤激光器机理研究

As the tunable multi-wavelength mode-locked fiber lasers（MLFL）could be used as a low-cost, convenient and practical tool of producing wide-range ultrashort pulse, they are suitable sources for a variety of applications and scientific research. In this project, an all-fiber multi-wavelength tunable MLFL based on topological insulator (TI) saturable absorber (SA) would be suggested and demonstrated. In the project, the SA made by TI would be used as the tools both to control laser mode competition in cavity and to form multi-wavelength mode-locked, which TIs possess broadband wavelength operation characteristic and giant third order nonlinear property. The research work would focus on the mechanism of formation and propagation of multi-wavelength ultrafast pulses, or solitons of MLFL, in which TI would function as both SA for mode-locked and nonlinear optical materials for multi-wavelength working. The laser gain controlling, mode competition adjusting, optimization and laser dynamics would be discussed. The multi-wavelength tunable MLFL would be developed and be optimized，which femtosecond pulses would be output. The simulation model of lasers would be built up and demonstrated. The new phenomena and questions found in the experiment would be studied also. This work would be helpful to the field of such as optical communication, fiber sensor and precise optical metrology. It is significance for research in ultrafast laser optics, optics of TI materials, nonlinear fiber optical also.

可调谐多波长超快光纤激光器作为低成本、方便实用的超短脉冲光源在诸多领域有广泛的应用前景。本项目提出利用拓扑绝缘体既具有宽带可饱和吸收又具有高光学非线性的优点构建可调谐多波长超快光纤激光器，前者用于锁模，后者用于抑制激光腔内模式竞争，实现多波长输出。我们研究该拓扑绝缘体双功能器件用于产生多波长超短脉冲的机制、多波长传统孤子和耗散孤子的演化规律、模式竞争和脉冲增益控制以及相关的超快激光动力学机理。项目将建立可调谐多波长超快激光器的仿真模型并实验验证，实现多波长超快脉冲输出，解决系统优化设计与实现中的关键技术问题，并对实验中发现的新问题进行研究和探索。本项目将会促进多波长超快光纤激光器在波分复用光通信、光纤传感、精密光学测量等领域的应用；对于超快激光光学、二维纳米材料光学、非线性光纤光学等方面的研究也有重要科学意义。

多波长被动锁模光纤激光器可用于波分复用通信等领域。拓扑绝缘体兼具可饱和吸收锁模和非线性光学材料双重功能，利用它制作的可饱和吸收体具有响应时间快、非线性强、宽波长范围等优点，可用于产生多波长超短锁模脉冲。 .我们利用非线性薛定谔方程和金兹伯格-朗道方程建立了激光器的物理模型。通过数值仿真可以得到主要参量的变化对实验结果的影响趋势，与实验结果基本一致。.我们利用拓扑绝缘体Bi2Se3实现了可调谐1～4波长锁模光纤激光激光器。在激光器的近零色散区实现了双波长亮-暗孤子对的基频和高次谐波运转，最高重复频率为433.8 MHz（280次谐波）。还实现了双波长混合类台阶-暗孤子脉冲以及双波长高能量矩形脉冲，脉冲能量为0.593 nJ～2.824 nJ，远高于传统孤子的脉冲能量。 .我们利用基于涂镀WS2材料的光纤拉锥体作为锁模器件，在激光器的负色散区，实现了双波长飞秒孤子以及“凹形边带”孤子。我们获得单波长孤子谱宽和脉宽分别为11.48 nm和220 fs；还首次获得了脉宽分别为605 fs和585 fs的双波长飞秒孤子。.我们搭建基于渐变多模光纤－阶跃多模光纤－渐变多模光纤类可饱和吸收体的锁模光纤激光器，输出重复频率为10.29MHz（基频运转），孤子脉宽为364fs；还实现了45次（462.96 MHz）和74次(763.36MHz)谐波锁模。理论上脉冲重复频率能在10.29MHz ～763.36MHz范围内可调谐。我们还成功的观测到了2～11阶连续可调高阶束缚态孤子。.本项目研究成果将会促进多波长超快光纤激光器在光通信、光纤传感、精密光学测量等领域的应用；对于超快激光光学、二维纳米材料光学、非线性光纤光学等方面的研究也有重要科学意义。