用于中红外超连续谱产生的高激光损伤阈值光稳定硫系玻璃光纤

Pumping high-nonlinearity chalcogenide glass fibers with ultrashort pulses is one of the important approaches to achieve broadband mid-infrared supercontinuum (MIR SC). Obtaining chalcogenide fibers with high laser damage threshold and excellent photo-stability (photo-induced refractive index is negligible) is crucial for generating stable high-brightness MIR SC and is also the current problem to be solved. This project proposes to study the laser damages and photo-induced refractive changes in chalcogenide glasses under irradiation of ultrashort pulses, and to explore the technical approaches on generating stable high-brightness broadband MIR SC in chalcogenide fibers. We will investigate the damage thresholds and the photo-induced refractive changes of chalcogenide glasses with different topological structures and chemical stoichiometry under irradiation of ultrashort pulses. We will reveal the interrelationship between these two parameters and the glass network structures, as well as the chemical bonds. We will also elucidate the mechanisms inducing these two phenomena and optimize the glass compositions accordingly for producing chalcogenide fibers with high laser damage thresholds and excellent photo-stability. We have made substantial progress in MIR SC generation in our recent work. This study will have important academic values to understanding the intrinsic relationship between the stability of MIR SC generated in chalcogenide fibers and the glass compositions. It is also expected to achieve practical MIR SC sources covering the 2-12μm spectral range using the developed chalcogenide fibers. These sources may be used in the applications such as early cancer diagnosis, chemical sensing and food quality control.

以超短脉冲泵浦高非线性硫系玻璃光纤是产生宽带中红外超连续谱（MIR SC）的重要途径，获得优异光稳定性（光致折射率变化极小）和高激光损伤阈值的硫系光纤是产生稳定的高亮度MIR SC的关键和亟待解决的问题。本项目拟开展硫系玻璃在超短脉冲辐照下的激光损伤和光致折射率变化研究，探索在硫系光纤中产生稳定的高亮度宽带MIR SC的技术途径。我们将研究具有不同拓扑结构和化学计量的玻璃在超短脉冲辐照下的激光损伤和光致折射率变化，揭示二者与玻璃网络结构和化学键的内在联系，阐明二者产生的机理，从而对玻璃组成进行调控，获得用于制备高激光损伤阈值光稳定硫系光纤的基质玻璃。我们前期工作已在硫系光纤中产生MIR SC方面取得重要进展。本研究对认识MIR SC的稳定性与玻璃组成的内在关系具有重要学术价值，同时有望获得基于硫系光纤的实用型2-12μm MIR SC光源，可用于癌症早期诊断、化学传感、食品安全控制等领域。

中红外（MIR）超连续谱（SC）光源具有光谱范围宽、亮度高、空间相干性好等优点，被认为是新一代高性能宽带MIR光源。本项目结合硫系玻璃优异的MIR透光性和超高的三阶非线性，提出研制一类光稳定的高激光损伤阈值硫系玻璃光纤，以其为非线性介质产生高亮度的宽带SC。主要实施的研究工作及获得的结果如下：.1. 考察了硫系玻璃的折射率(n)、热光系数(ζ)、密度(d)和体积膨胀系数(β)随化学组成的变化。获得了玻璃的n与d和组成元素摩尔折射度（Ri）之间的定量关系，以及玻璃的ζ与β和组成元素摩尔折射度温度系数（φi）之间的定量关系。该研究对红外硫系玻璃的n和ζ的预测与调控具有一定指导意义和科学价值。.2. 采用飞秒激光辐照硫系玻璃，研究了玻璃激光损伤阈值与玻璃化学组成的关系，以及不同重复频率超短脉冲辐照下对应的损伤机理。该研究对非线性光学中的玻璃材料成分选择和抽运方案设计具有一定指导意义和科学价值。.3. 开发了一种新型Ga-Sb-S硫化物玻璃，与目前研究较成熟的Ge基和As基硫化物玻璃相比，该玻璃具有更宽的红外透光范围和更高的三阶非线性折射率，是一种极具应用潜力的中红外三阶非线性材料。.4. 制备了小芯径阶跃折射率硫系光纤、长方形芯硫系光纤、凸型芯硫系光纤，研究了光纤中MIR SC的产生。在优化的硫系光纤中产生了覆盖2-12 µm的超连续谱，最高平均功率约20 mW。该研究对认识非线性硫系光纤中SC的产生具有一定学术价值。研制的小芯径硫系光纤已被国内外多个科研单位用于非线性光学、光学传感等领域。.5. 为了进一步提高硫系玻璃光纤可承受的激光功率，从而提高光纤中可输出的SC的平均功率，设计并制备了超大模场全固态硫系玻璃光子晶体光纤，研究了光纤的损伤和超连续谱的产生。该研究为获取高亮度MIR SC光源提供了新的途径。