基于硫系材料的全光纤化宽带平坦中红外超连续谱光源研究

Broadband and flattened mid-infrared supercontinuum(SC) is a powerful way to achieve high-quality mid-infrared optical frequency comb. The bandwidth and flatness of mid-infrared SC are generally difficult to balance, and the selection of pump source is also limited. To alleviate these issues, the generation of broadband and flattened mid-infrared SC by using a fiber laser with 2-3μm SC output and a chalcogenide microstructured fiber is proposed. This project focuses at two key scientific issues: the collaborative optimization of dispersion and nonlinearity in the pump source(2-3μm SC fiber laser), and the mode field matching between silica fiber and chalcogenide microstructured fiber. In this project, a pump source will be designed and optimized, the efficient coupling between the silica fiber and the chalcogenide microstructured fiber, and the performance of the all-fiber mid-infrared SC source will be investigated. Through aiming at clarifing the physical mechanism and regulation mechanism of dispersion and nonlinear effects in chalcogenide fiber based mid-infrared SC source, and resolving the key technology of high efficient coupling between silica fiber and chalcogenide microstructured fiber, the project will provide an all-fiber mid-infrared SC source with 10dB bandwidth covering 2-5μm, and lay a solid scientific foundation for the application of mid-infrared laser in optical frequency comb and other research fields.

宽带平坦中红外超连续谱（SC谱）是高质量中红外光频梳的重要产生方式之一。针对现有中红外SC谱光源带宽和平坦度难以同时兼顾以及泵浦源选择存在局限性的弊端，本项目提出利用2-3μm SC谱输出的光纤激光器泵浦与之匹配的硫系微结构光纤产生宽带平坦中红外SC谱的方案，围绕泵浦源（2-3μm SC谱光纤激光器）色散与非线性调控、石英光纤与硫系微结构光纤模场匹配两个关键科学问题，通过对泵浦源设计与优化、石英光纤与硫系微结构光纤高效耦合以及全光纤化中红外SC谱光源的性能进行研究，旨在阐明硫系光纤中红外SC谱光源中色散与非线性作用的物理机理和调控机制，解决石英光纤与硫系微结构光纤模场匹配进而获得高效耦合的关键技术，最终实现10dB带宽覆盖2-5µm波段的全光纤化中红外SC谱光源，为中红外激光在光频梳等研究领域的应用奠定坚实的科学基础。

本项目针对中红外波段分子探测对中红外光频梳的应用需求。立足自主创新，攻关基于硫系材料的全光纤化宽带平坦中红外SC谱光源的关键技术。以理论分析和实验研究为主，从泵浦源设计与优化、石英光纤和硫系光纤高效耦合和中红外SC谱光源性能研究三方面入手。通过分别利用自制硫系悬吊芯光纤、商用ZBLAN光纤和商用硫系光纤作为非线性光纤，最终研制出三种不同特征的中红外宽带平坦SC谱光源。自制硫系悬吊芯光纤产生了波长覆盖2.0～6.95μm的中红外SC谱。商用ZBLAN实现了5.4W的1.9~4µm的中红外SC谱光源，光谱平坦性好，光谱强度变化在1.9~3.54µm只有0.09dB。基于商用的As2S3光纤实现0.9W的1.9~3.5µm的中红外SC谱光源，这些方案为中红外激光在光频梳等研究领域的应用积累了丰富的技术储备。