过渡金属硫化物/二氧化硅复合型光学器件制备及应用研究

In recent years, because of the fast carriers and excellent nonlinear optical properties, the two-dimensional transition metal dichalcogenides (TMDs) have become the hot spot in ultrafast photonics research. Especially it shows great potential in the field of saturable absorbers (SAs) applications. But the preparation methods and technology are still not perfect, the research on TMDs SAs are limited to material level studies. This proposed project will prepare the evanescent wave TMDs/SiO2 SA devices by sol-gel method combined with D-shaped fiber. This project would study the morphology characteristics and mechanical properties. The theoretical and experimental researches will be carried out to study the adjustable nonlinear parameters (modulation depth, nonsatrable losses and damage threshold) of TMDs/SiO2 SA devices. Based on these SA devices, we will also construct the erbium and ytterbium doped all-fiber lasers to study the long-term stability and analysis the variation of fiber laser parameters (pulse width, output power et al.), realizing the ultrashort femtosecond pulses and high power pulses output. The TMDs nano-sheets distribution in silica substrate can not only isolate air and avoid oxidation effectively, but also enhance the mechanical performance of SA devices. By adopting the laser evanescent wave interacts with TMDs materials, it can improve the damage threshold of TMDs SA devices to a great extent. This proposed project belongs to the interdisciplinary investigation, including the TMDs materials study and ultrafast laser technology research, which would promote the integrated research of materials → devices → lasers.

近些年来，二维过渡金属硫化物(TMDs)因其超快载流子特性和优异的非线性光学等特性成为超快光子学领域的研究热点。因制备技术不够完善，国内外关于其可饱和吸收体方面的应用研究多是限于材料层面研究。本项目拟采用溶胶凝胶法结合D型光纤制备倏逝波型过渡金属硫化物/二氧化硅可饱和吸收体器件，研究其表观和机械性能，从理论和实验系统探索吸收体器件非线性参数（调制深度、非饱和损耗、损伤阈值等）可调特性。基于制备的吸收体器件，搭建掺铒和掺镱全光纤激光器，研究激光器输出参数（脉宽、功率等）随吸收体器件非线性参数变化规律，实现超短飞秒脉冲和高功率脉冲输出。TMDs纳米片分布在二氧化硅基质中，可以有效地隔绝空气避免氧化，增加器件机械性能。采用倏逝波方法，避免激光与材料直接作用，从而提高器件损伤阈值。本项目属于交叉学科研究，包含TMDs材料和超快激光技术两方面研究，将推动材料→器件→激光器一体化应用研究。

近些年来，由于在兼容性、灵活性和光束质量方面的优异性，新型二维材料脉冲光纤激光器已成为超快光子学领域的研究热点。可饱和吸收体是光纤激光器中获得超短脉冲输出的关键非线性光学器件，目前应用较多的半导体可饱和吸收镜存在制备工艺复杂、成本高、工作波长范围窄（<100 nm）等限制。随着石墨烯的发现及其奇异特性的不断挖掘，二维材料开始进入人们的视野，并引起越来越多的关注。二维过渡金属硫化物纳米材料因其超快载流子特性、工作波长范围宽、调制深度大等特性成为一种极有潜力的非线性光学材料。因其制备技术不够完善，国内外关于二维过渡金属硫化物可饱和吸收体方面应用研究多是限于材料层面研究。如何提高二维材料制备的质量及其性能，并在全光纤激光器中获得高功率窄脉宽输出是目前需要研究的课题。本项目使用溶胶凝胶法和液相剥离法等方法，结合D型光纤和拉锥光纤，依据倏逝波原理，制备得到了具有高损伤阈值和非线性参数可调的倏逝波型可饱和吸收体器件，并研究了其材料、表观和光学特性等，全面分析了可饱和吸收特性。通过改变D型光纤和拉锥光纤参数以及纳米片材料厚度等因素实现了对可饱和吸收体非线性的调控，器件的调制深度在5%-50%之间可调。通过溶胶凝胶法制备的复合型可饱和吸收体的损伤阈值被提高到了3.46J/cm2，较以往的器件有所提高。此外，本项目也从实验方面实现了对超短脉冲激光产生的研究。基于所得到的倏逝波型TMDs可饱和吸收体，通过优化腔内的色散分布，在掺铒全光纤激光器中实现了平均输出功率为23.34 mW的飞秒(709 fs)孤子脉冲输出。本项目在深入研究二维TMDs的同时，进一步提高了可饱和吸收体光学器件的性能，推动了材料→器件→激光器一体化应用研究。