基于二维过渡金属硫化物的光学器件制备及性能研究

Since the beginning of graphene, broadband saturable absorber based on two-dimensional materials become the hot spot in ultrafast photonics research. But the preparation technology and optical properties are not mature, and the lower damage threshold and slow recovery time are the main factors to restrict mode-locked pulses with narrow pulse duration and high energy in fiber lasers. The pulsed laser deposition (PLD) method will be employed in this research. The two dimensional transition metal dichalcogenides (TMDs) with ultrashort electron relaxation time and high damage threshold will be used as the saturable absorption materials. The saturable absorbers with high damage threshold and ultrafast recovery time will be prepared. Besides, the properties of material, apparent and ultrafast laser for two dimensional TMDs saturable absorbers will be characterized. In addition, based on those saturable absorbers with different characteristics, theoretical and experimental researches will be carried out to construct the ytterbium doped fiber laser with high energy and the erbium doped fiber laser with high repetition frequency and narrow pulse duration, respectively. Those applications in fiber laser can confirm that the saturable absorbers can be used for mode locking at several bands, and have such characteristics as the high damage threshold and ultrafast recovery time. This issue not only focuses on the two dimensional TMDs study, but also includes the research on basic devices and ultrafast laser technology, which will be helpful to enhance the applications of two-dimensional materials in optical communication, laser processing and high precision measurement, etc.

自石墨烯开始，基于新型二维材料的宽带可饱和吸收体研究成为超快光子学的研究热点。但其制备技术和光学性能还不成熟，较低的损伤阈值和较慢的恢复时间是制约光纤激光器窄脉宽和高能量锁模脉冲输出的主要因素。本项目将使用脉冲激光沉积（PLD）法，利用具有超短电子弛豫时间和高损伤阈值的二维过渡金属硫化物（TMDs）作为可饱和吸收材料，制备高损伤阈值和超快恢复时间的可饱和吸收体。在此基础上进一步表征其材料特性、表观特性和超快激光特性等。此外，基于不同特性的二维TMDs可饱和吸收体，本项目将在理论和实验上系统研制高重频、窄脉宽掺铒光纤激光器和高能量掺镱光纤激光器。从而验证该类可饱和吸收体可用于多段波锁模，并且具有高损伤阈值和超快恢复时间的特点。本项目在深入研究二维TMDs的同时，又包括了基础器件及其超快激光技术的研究，有助于加强二维材料在光通信、激光加工和高精密测量等领域的应用。

近年来，由于在稳定性和光束质量方面的优异性，基于新型宽带二维材料可饱和吸收体的光纤激光器成为了超快光子学的研究热点。但是该类激光器由于极大依托于二维材料的非线性，所以容易受到材料质量和热损伤等问题的桎梏，从而影响脉冲激光的稳定性和脉宽等。因此如何在选择高性能的二维材料的同时，进一步提高二维材料制备的质量和相应可饱和吸收体的性能，从而得到窄脉宽和高功率锁模脉冲输出是目前面临的主要挑战。本项目使用脉冲激光沉积（PLD）和化学气相沉积（CVD）等方法，选择具有超短电子弛豫时间和高损伤阈值的二维过渡金属硫化物（TMDs）材料作为功能材料，通过反复改进实验参数，制备得到了具有高损伤阈值和超强非线性的可饱和吸收体。并且在此基础上通过进一步表征其材料、表观和光学特性等，全面分析了可饱和吸收体的光电特性。表征结果表明，相应可饱和吸收体的损伤阈值一度被提高到了 14.13J/cm^2，较以往的器件提升了四个数量级。另外，通过改进制备方法以及改变材料厚度等因素成功实现了对可饱和吸收体非线性的调控，器件的调制深度最大超过了65%，在以往的基础上有了大幅度的提高。此外，本项目也从理论和实验两个方面实现了对超强超短脉冲激光产生的研究。基于所得到的高性能的二维TMDs可饱和吸收体，通过优化腔内的色散分布，本项目在掺铒光纤激光器中得到了67fs的超短脉冲输出，该结果创造了同类激光器的最短记录。在掺镱激光器中，基于高损伤阈值的可饱和吸收体得到了输出功率高达1.6W，脉冲宽度为110fs的锁模脉冲输出。掺铒和掺镱激光器的实现验证了该类可饱和吸收体可用于多波段锁模，并且具有高损伤阈值和强非线性的特点。本项目在深入研究二维TMDs的同时，进一步提高了基础光学器件的性能，加深了对于相应激光器的研究，满足了目前人们对于超强超快激光的应用需求，推动了二维材料在光通信、激光加工和高精密测量等领域的应用。