多芯分段错位掺杂微结构光纤的制备及其特性研究

The rapid development of high power fiber laser technology and products in the world promoted the application of high power fiber lasers in industrial processing in China. The structures of high power fiber lasers and their key components - doped fibers are developed in the United States and a few European countries, as a result, doped fibers and manufacturing of high power fiber lasers have to be imported from foreign countries. Doped PCF structure design and manufacturing techniques became a bottleneck of development of high-power micro-structured fiber lasers. In order to overcome this problem and to realize high-power micro-structured fiber lasers with doped PCF made in China, studied on high-power fiber lasers are very necessary. This project adopted theory analysis and experiment technical route. First, laser self-organized coherent could gain by evanescent wave coupling of doped multi-core. Second，using piecewise dislocation and rotating pulling could gain doping concentration gradient along the fiber of micro-structure fiber in order to improve the laser output intensity of high power fiber lasers. Third,based on the Rsoft simulation tools, the relations among core numbers, core distance, doping concentration, doping length, rotation angle and dislocation distance were studied. Finally, using an improved intelligent control system, we completed from preform to PCF with small fiber degradation. With low-loss fusion splice of PCF into a fiber laser system using a pressure-aided method, we realized high-power laser output.

近年来，快速发展的高功率光纤激光器技术推动了高功率光纤激光器在科学研究、国防和工业加工中的应用，而高功率光纤激光器的核心元件-掺杂光纤的结构设计和制备工艺只为欧美少数国家所掌握，这成为限制我国高功率光纤激光器发展的瓶颈。微结构光纤由于其灵活的结构设计和高度可调的光学特性在高功率光纤激光器的研发中具有独特的优势。本项目采用理论分析与实验制备相结合的技术路线，首先在理论上分析利用多掺杂芯间倏逝波耦合实现激光自组织相干，利用分段错位掺杂、旋转拉制实现微结构光纤沿光纤轴向掺杂浓度渐变进而有效提高高功率光纤激光器的激光输出强度。其次基于Rsoft软件模拟寻求最佳的芯数、芯距、掺杂浓度、掺杂长度、旋转角度和错位距离。最后根据理论设计制作光纤预制棒，进一步利用光纤拉丝系统完成多芯分段错位掺杂微结构光纤的制备，在压力辅助下实现微结构光纤低损耗熔接进激光系统，实现高功率激光输出的目标

高功率光纤激光器在军事、工业等领域的广泛应用，使得高功率光纤激光器的研发成为欧美国家项目支持的重点。微结构光纤(MSF)的诞生为人们制作光纤有源器件提供了一种新的载体。掺杂MSF作为高功率微结构光纤激光器(MSFL)的理想放大器件具有许多奇异的光学特性，而这些正是传统掺杂光纤激光器所不能获得的。在追求MSFL高功率输出的道路上，本项目期望实现高光束质量、高平均功率、高峰值功率的三高愿望，将三高性能能集于一身的MSF作为放大器件。主要研究内容包括多掺杂纤芯基于倏逝波耦合实现自组织相干有效提高激光输出功率，按掺杂浓度不同分段、错位排列和旋转拉制实现掺杂浓度沿光纤渐变，最终同时提高平均和峰值功率。多芯、分段、错位排列的设计想法在预制棒制备时就已经排布完成回避了后期熔接问题，这样的MSF可以实现三高集于一身，有效提高激光器输出功率且减小热效应的限制。本项目完成了3芯、7芯、19芯的多芯、分段、错位预制棒的材料制备和设计，完成了3芯、7芯、19芯的微结构光纤拉制，完成了对上述光纤样品的激光性能测试，完成了光纤熔接实验测试和热效应测试。多芯光纤的成功拉制从理论和实验上证明了方案的可行性和稳定性，其中7芯的光光转化效率达到76%，基本与国际主流多芯光纤激光性能相当，高功率相干输出的目标可以认为基本实现。对光纤熔接进行实验测试，熔接损耗基本控制在93%以上，可以满足工业及工程实际需求。基于上述研究工作，在稳定工艺的同时进行了高低温老化实验，更加利于产品批量生产稳定性和工业落地时技术可操作性。