高功率全光纤激光器光纤耦合关键技术研究

发布时间：2018-07-31 13:46

【摘要】：高功率全光纤激光器的关键技术主要有:半导体泵浦源技术,双包层光纤技术,光纤耦合技术,光纤光栅及终端输出技术。其中,光纤耦合技术作为激光器的核心技术之一,其目的是要将泵浦光或信号光高效地耦合到双包层光纤。总的来说,光纤耦合技术主要有两种:锥形光纤束端面耦合技术和侧面光纤耦合技术。然而,目前用于高功率条件下的光纤耦合器大多需要国外进口。因此,研制国产高功率光纤器件及基于国产器件的高功率光纤激光器对中国光纤激光技术的发展具有重要的战略意义。主要对几种特殊波导光纤的模场特性、锥形光纤束端面光纤耦合技术和侧面光纤耦合技术进行了理论和实验研究。本论文的主要研究内容和成果包括以下几个方面:1、利用光束传播法分析了弯曲光纤、锥形光纤和热扩芯光纤的模场分布特性及光束传输特性,并采用热扩芯技术研制出百瓦级光纤模场匹配器。首先,研究了大模场面积光纤的抗弯曲特性,并分析了由光纤弯曲导致的光场畸变。结果表明,光纤模式阶数越高,对弯曲越敏感;光纤弯曲半径越大、折射率差越小、芯径越大,畸变越严重;其次,分析了锥形光纤的模场分布特性和低损耗拉锥条件。结果表明:对单模光纤,只要满足绝热拉锥条件就能获得高的传输效率;而对多模光纤,影响其传输效率的因素主要是拉锥比;最后,重点对热扩芯光纤的模场分布特性进行了研究。理论模拟和实验发现,与单模光纤相比,热扩芯时大模场面积光纤的模场直径增大的更快。另外,对光束在热扩芯光纤中的传输特性的分析结果表明,即使实现了不同光纤模场直径之间的匹配,光纤模场匹配器的传输损耗依然存在。实验上采用6/125μm单模光纤和15/130μm大模场面积光纤自行研制了百瓦级光纤模场匹配器,其通光效率74%,承受功率大于100W,性能优于市场上同等规格的商用光纤模场匹配器。最后,热扩芯技术还可用于光纤耦合器的制备。2、基于热扩芯技术,提出一种针对大包层-纤芯比准单模光纤功率合束的方法——过渡光纤法,解决了高功率单模光纤激光器模块的功率合束问题,并研制了千瓦级N×1型泵浦光合束器及信号光合束器。首先,对N×1型泵浦光纤合束器进行了理论和实验研究。基于Vytran GPX系列光纤处理平台,采用锥形光纤束石英套管法,制作完成了3×1、7×1、19×1及61×1四种高功率泵浦光纤合束器;其次,对N×1型单模信号光纤能量合束器进行了理论和实验研究。分析了7×1单模信号光纤能量合束器的模场分布和光传输特性,重点分析了空间瞬态对合束器传输效率的影响。采用基于热扩芯技术的过渡光纤法制备了7×1型信号光合束器,并将7路600W单模激光合束,获得了4k W的激光输出。3、自主研制了高功率(N+1)×1型侧面泵浦光耦合器,并采用自行研制的侧面泵浦光耦合器,搭建了侧面多点泵浦全光纤结构主振荡功率放大器。首先,对熔锥型侧面泵浦光耦合器进行了理论研究,实验上采用石墨灯丝加热法研制出了(2+1)×1熔锥型侧面泵浦光耦合器,该耦合器的耦合效率为94%,单臂可承受200W泵浦功率;其次,对角度磨抛侧面熔接泵浦光耦合器进行了理论分析与模拟。实验上采用CO2激光熔接的方式,自行研制了(1+1)×1型角度磨抛侧面泵浦光耦合器,该耦合器的耦合效率高达97%,信号光插损小于2%,可承受最高140W的泵浦功率;最后,对侧面多点泵浦耦合方式下光纤放大器的光功率分布进行了数值模拟,分析了侧面分布泵浦耦合方式下单个耦合器的性能以及耦合器的分布方式对光纤放大器效率的影响。4、基于主振荡功率放大结构,采用自行研制的N×1型泵浦光合束器,搭建了千瓦级掺Yb双包层光纤放大器。分析了激光器的热效应及影响激光器输出光束质量的因素。最终获得了稳定的1.02k W基模连续激光输出和较好的光束质量M2=1.07,并制作了激光器样机用于金属切割。另外,采用自行研制的角度磨抛侧面泵浦光耦合器,搭建了侧面多点泵浦、掺Yb双包层光纤主振荡功率放大器。实验上,采用8个级联(1+1)×1型侧面泵浦光耦合器对放大级光纤进行泵浦,最终获得了303W的功率输出,激光器放大级光-光转换效率达到57%。
[Abstract]:The key technologies of high power all fiber laser are: semiconductor pump, double clad fiber, fiber coupling, fiber Bragg grating and terminal output. Among them, optical fiber coupling technology is one of the core technologies of laser. The aim is to effectively coupling the pump light or signal light to double clad fiber. There are two main kinds of optical fiber coupling technology: cone fiber beam end coupling technology and side fiber coupling technology. However, most of the optical fiber couplers used in high power conditions need to be imported abroad. Therefore, the development of domestic high power fiber devices and high power rate fiber laser based on domestic devices for Chinese optical fiber laser technology is developed. The main research contents and results in this paper are as follows: 1, the bending fiber and conical fiber are analyzed by the beam propagation method. The mode field distribution characteristics and beam transmission characteristics of the hot diffused core fiber are presented, and a 100 watt fiber mode field matching device is developed with the heat expansion core technology. First, the anti bending characteristics of the large mode field area fiber are studied and the optical field distortion caused by the optical fiber bending is analyzed. The results show that the higher the mode order of the fiber is, the more sensitive to the bending and the fiber bending. The larger the radius, the smaller the refractive index difference, the larger the core diameter, the more serious the distortion. Secondly, the mode field distribution and the low loss taper condition of the conical fiber are analyzed. The results show that the high transmission efficiency can be obtained by satisfying the adiabatic taper condition for the single mode fiber, and the main factors affecting the transmission efficiency of the multimode fiber are the taper ratio; finally, the factors that affect the transmission efficiency are the last. The distribution characteristics of the mode field of the hot expanding core fiber are studied. The theoretical simulation and experimental results show that the mode field diameter of the large mode field area fiber increases faster than the single mode fiber. In addition, the analysis results of the transmission characteristics of the beam in the thermal diffuser fiber show that even the diameter of the different optical fiber field is realized. The transmission loss of the optical fiber mode field matcher still exists. In the experiment, the 6/125 mu m single mode fiber and the 15/130 mu m field area fiber are used to develop a 100 watts mode field matching device. The optical efficiency is 74%, the power is more than 100W, and the performance is better than the same specification in the market. Finally, the hot expanding core technology It can also be used in the preparation of.2 for fiber couplers. Based on the technology of thermal expansion, a method of transition fiber is proposed, which aims at the high power bundle of core ratio quasi single mode fiber power beam. The power closing of high power single-mode fiber laser module is solved, and a kilowatt level N x 1 type pump beam splitter and a signal beam splitter are developed. The theoretical and experimental study of the N * 1 pump fiber beam splitter is carried out. Based on the Vytran GPX series optical fiber processing platform, the tapered fiber bundle quartz casing method is used to make 3 x 1,7 x 1,19 x 1 and 61 x 1 four high power pumping fiber bundles. Secondly, the theoretical and experimental Study on the N x 1 single mode signal light fiber energy beam splitter is carried out. The mode field distribution and optical transmission characteristics of the 7 x 1 single mode signal optical fiber energy beam splitter are analyzed. The effect of space transient on the transmission efficiency is analyzed. The 7 x 1 type of signal beam splitter is prepared by the transition fiber method based on the thermal expansion technology, and the laser output.3 of the 7 600W single mode laser is obtained, and the independent development of the laser output.3 is obtained. The high power (N+1) x 1 side pump coupler and the self developed side pump optical coupler have built the side multipoint pumped all fiber structure main oscillating power amplifier. First, the taper profile side pump coupler was theoretically studied. In the experiment, the (2+1) x 1 conical side profile was developed by the graphite filament heating method. The coupling efficiency of the pump coupler is 94%, the single arm can withstand the power of 200W pump. Secondly, the angle grinding and throwing side weld pump coupler is theoretically analyzed and simulated. In the experiment, a (1+1) x 1 angle grinding side pump coupler is developed by CO2 laser welding, and the coupling efficiency of the coupler is developed. Up to 97%, the signal light insertion loss is less than 2%, can withstand the maximum 140W pump power. Finally, the optical power distribution of the fiber amplifier under the side multi point pump coupling mode is numerically simulated, and the performance of the single coupler and the influence of the coupling device distribution mode on the efficiency of the fiber amplifier are analyzed by the side distribution pump coupling mode.4, Based on the main oscillator power amplification structure, a self developed N x 1 type pump beam splitter is used to build a kilowatt class Yb double cladding fiber amplifier. The thermal effect of the laser and the factors affecting the output beam quality of the laser are analyzed. Finally, the stable 1.02k W base mode continuous excitation output and the better beam quality M2=1.07 are obtained. The laser prototype is used for metal cutting. In addition, the side multipoint pump and Yb double cladding fiber main oscillating power amplifier are built by the self developed angle grinding and polishing side pump optical coupler. In the experiment, 8 cascaded (1+1) x 1 side pump optical couplers are used to pump the magnified fiber, and the power of 303W is finally obtained. Output, laser amplifier, optical to optical conversion efficiency of 57%.
【学位授予单位】：北京工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN248

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