中红外硫系玻璃微球激光器的研究

Mid-infrared lasers have many important applications in the fields of bio-sensing, spectroscopic analysis, and non-linear optics. In this project, we propose developing a mid-infrared microsphere laser using Rare-earth Element Ion (REI) doped chalcogenide glasses as base materials. This new laser design combines the advantages of chalcogenide glasses (such as high solubility of REIs, high transmissivity in the infrared spectrum, and high refractive indices) and those of microsphere resonators (such as small volumes and high quality factors), and thus it possesses many desirable characteristics in the mid-infrared spectrum, such as low pump thresholds and narrow linewidths. To implement this project, we will develop chalcogenide fiber tapers for coupling the pump light into microspheres. Designs of chalcogenide fiber tapers and microsphere resonators will be optimized according to the Mie scattering theory and electromagnetic theory so that the efficiency of the coupling system can be enhanced. According to the thermal-dynamic properties of chalcogenide glasses, we will optimize the distribution of heating zones and the flow-rates of protective gases in the sphere-making furnace, such that the surface quality, sphericity, and throughput of microspheres can be improved. We will also ascertain the theoretical mechanism of the laser-line shifting phenomenon caused by thermal effects of the pump light and propose proper temperature-controlling methods to stabilize those laser-lines. By implementing this project, we could gain new understandings in the coupling theory of microspheres/fiber tapers, making new progresses in the fabrication technique of chalcogenide microspheres, and clarify the laser-line shifting mechanism in microsphere lasers. This project also provides a new approach of utilizing chalcogenide glasses in the infrared opto-electrical industry.

中红外激光器在生物传感、光谱分析、非线性光学等领域有广泛的应用。本项目提出研究一种基于稀土离子掺杂硫系玻璃的中红外微球激光器，旨在将硫系玻璃良好的稀土溶解性、优良的红外透过性、较高的折射率等优点与微球谐振腔的小体积能耗、高品质因数等优点相结合，实现一种低泵浦阈值、窄谱线带宽的微型中红外激光器。本项目拟采用硫系玻璃光纤锥以倏逝波的形式为硫系微球导入泵浦光，通过米氏散射理论和模式耦合理论优化微球和光纤锥的设计，提升泵浦耦合效率；拟根据硫系玻璃的热力学特性优化制球炉具的温度分布以及保护气体流速等参数，提升微球表面质量、球形度以及产量；拟通过微腔电磁场理论探明微球在泵浦光热效应作用下激光谱线平移的机理，并设计合理的温控装置提升微球激光输出的稳定性。通过本课题的研究，有望在微球谐振腔耦合理论、硫系微球制备及微球激光谱线平移机理等领域取得新的研究进展，为硫系玻璃在红外光电领域的应用提供一种新的思路

中红外激光器在生物传感、光谱分析、非线性光学等领域有广泛的应用。本项目主要利用了硫系玻璃/碲酸盐玻璃等新型红外材料制备了工作于2微米附近中红外波段的微型回廊模谐振腔，并探索了此类谐振腔在温度传感领域的应用。考虑到硫系玻璃在高温时容易出现的析晶问题，本项目选用了加工温度相对较低的漂浮粉末熔融法制备微球谐振腔，自制了相关的加热炉具，并选取了一种低熔点硫系玻璃（Ge-Ga-Sb-S玻璃，简称2S2G玻璃）作为微球制备的基质材料，在约650oC的较低温度下成功制备出品质因数（Q值）大于十万的微球谐振腔，并验证出这些微球的回廊模谐振峰有28pm/oC的温度响应特性。在此基础上，本项目一方面积极开展优化硫系玻璃微球质量的研究工作；一方面探索使用碲酸盐玻璃作为2微米微球谐振腔的替换材料。项目组利用气氛保护的漂浮粉末熔融装置制备出了Tm3+离子掺杂的2S2G硫系玻璃微球谐振腔，成功表征出了1.9微米附近的微球激光峰和约29.56pm/oC的温度传感特性。项目组也分别利用了Tm3+-Ho3+共掺的硫系玻璃和碲酸盐玻璃制备出了可激发出2微米附近激光峰的中红外微球激光器。针对微球激光器泵浦效率不高的问题，项目组发现了微球在光纤锥耦合泵浦时会发生一种折射漏光现象，并探究了一种利用金属漫反射面控制漏光的实验方法，提升了微球的泵浦效率以及降低了微球激光的阈值。项目组也利用了碲酸盐玻璃具有较为稳定的热学特性的优点，研究了在微球谐振腔的基础上采用一种自制热压装置制备微盘谐振腔的工艺方法，成功制备出了Q值在十万以上，且可以激发出2微米附近激光的微盘激光器。相对于微球激光器，微盘激光器具有更小的模式体积，可更有利于微球与其它微纳光子器件的耦合以及更容易在微腔中实现光学非线性效应。