液相沉积金属毛细管氧化锗空芯光纤及其激光传输可靠性研究

We intend to fabricate germanium dioxide hollow optical fiber with higher reliability for delivery of carbon dioxide laser beam by substituting a robust metal pipe for a conventional silica glass tube. Flexible, robust metallic pipes with high melting points as well as low chemical reactivity are selected as structural tubes. The inner wall of the metal pipe will be polished using a pulse high-pressure driven fluid containing micro- to nano-meter sized solid particles. An alumina buffer layer is coated on the inner tube wall using an aqueous alumina sol. A homogeneous liquid phase deposition (LPD) process is used to grow germanium dioxide reflective films inside the tubes at room temperature. A hollow waveguide sample can be obtained after densification of the germanium dioxide film at a temperature close to its melting point. The type and size of the metal pipe will be carefully designed. We will also develop a proper method to polish the metal pipe. The alumina buffer layer and its behaviors in improvement of the quality of the LPD-derived germanium dioxide film and oxidation resistance of the metal pipe will be studied. This project also aims at analyzing the properties and rules of the laser beam transmitted through the metal pipe germanium dioxide optical fiber. We expect to establish the principles and find the key techniques for preparing a metal pipe germanium dioxide hollow fiber with higher reliability for laser beam delivery. The rules relating to the reliable transmission of carbon dioxide laser will be disclosed. The current research project may provide theory and technique supports for applications of carbon dioxide laser radiation in infrared detector, laser surgery, spin-manipulation of narrow band gap semiconductors, long-wavelength information transmission, laser ignition and material processing.

本项目探索用力学和散热性能更好的金属毛细管代替传统石英玻璃毛细管制备传输二氧化碳激光可靠性更高的氧化锗红外空芯光纤。选择柔韧、高熔点和低化学活性金属毛细管（镍、铌、钽合金等），用内循环高压脉冲微纳粒子流体抛光管内表面，在管内壁上用水性溶胶制备氧化铝缓冲层，通过室温液相沉积在管内生长氧化锗反射膜，将膜原位熔融致密化后得到光纤。本项目拟通过金属毛细管材质尺寸优化设计、毛细管内抛光机制、用氧化铝缓冲层调控沉积氧化锗膜和阻止金属管内表面热氧化、光纤传输激光性质和可靠性规律等方面的研究，获得有较高可靠性金属毛细管氧化锗空芯光纤的研制原理和技术，揭示这类光纤传输二氧化碳激光的可靠性规律，为促进二氧化碳激光在红外探测、激光生命医疗、窄禁带半导体电子自旋调控、长波红外信息传输、激光点火、材料成型加工等领域的深入应用提供提供理论和技术支持。

本项目研究尝试用力学和散热性能更好的金属毛细管代替传统石英玻璃毛细管研制更高可靠性金属毛细管空芯光纤。主要探讨光纤的力学可靠性设计原理、金属毛细管内抛光机制、液相调控沉积生长氧化锗反射膜、光纤的光学传输性能和规律、光纤热学可靠性评估和安全操控机制、金属毛细管空芯光纤潜在应用等方面的内容。建立了金属毛细管空芯光纤力学可靠性设计模型并通过实验验证，设计并定制出了具有力学可靠性（18cm半径以上无损弹性弯曲）和热学可靠性的铜、镍、不锈钢、镍铬和钛五种材质的金属毛细管；获得了以氧化、络合和氧化铝纳米流体作用为基础的金属毛细管内抛光方案，将管内表面粗糙度由2-11μm降至0.7μm以下。通过诱导析晶、氧化锗沉积次数和衬底晶型及热膨胀系数匹配等操控优化制备出了五种材质金属毛细管空芯光纤。所研制的光纤传输CO2激光实测直线损耗低至0.2dB/m，弯曲损耗低至1.9dB/m，输出光束发散角10-35mrad。基于转移矩阵射线模型计算与光束质量分析实验均表明金属毛细管光纤直线传输仍以HE11模为主，弯曲传输高阶模增加。基于流体热学、传热学和空芯光纤MS理论建立了金属毛细空芯光纤温度分布和传输激光功率可靠性评估和安全操控模拟软件。光纤的耦合损耗和高阶模间干涉作用使纤体温度沿轴向呈周期性振荡减小的分布状态。将不锈钢毛细管光纤传输激光功率控制在23W以下可避免纤体误烫伤人体（温度<47oC），实现医疗激光可靠性传输；将输入激光功率控制在1078W以下可实现Ni-Cr毛细管空芯光纤在激光点火、铁电氧化物材料生长、3D打印等高功率激光传输应用中的可靠性运行。通过充入氮气消除水蒸气凝结可使金属毛细管光纤在77K低温仍具有光学传输可靠性，能应用于低温光学诱导半导体电子自旋调控和化学传感研究。基于钛和不锈钢毛细管空芯光纤氧化物反射膜液相沉积生长和金属毛细管光纤限光特性的研究还获得了新型高光捕获性金属毛细管空芯光纤电池和复杂体系铁电氧化物材料的设计和制备技术。项目研究中还对具有ATR和Leaky双传输机制的中、远红外（太赫兹）金属毛细管氧化锗空芯光纤的研制可行性进行了积极探索。