基于分布式侧面耦合包层泵浦光纤的高功率超荧光光源研究

发布时间：2018-06-23 18:00

本文选题：超荧光 + 放大自发辐射　；参考：《国防科学技术大学》2015年硕士论文

【摘要】：超荧光光纤光源是利用稀土元素掺杂光纤中的放大自发辐射(ASE)过程获得宽谱输出的光纤光源,随着输出功率的不断提升,在不同领域得到广泛应用。分布式侧面耦合包层泵浦(DSCCP)基于倏逝场耦合技术,实现泵浦功率的分布耦合,有望实现超荧光输出功率的进一步提升。本文提出基于DSCCP光纤的超荧光光源设计方案,并建立基于DSCCP光纤的超荧光光源数值模型,分析其输出特性和功率提升限制因素,并通过优化实验设计,获得高功率输出的全光纤超荧光光源。论文主要工作如下:1.基于DSCCP光纤的超荧光光源理论研究和数值仿真根据DSCCP光纤的简化的泵浦光耦合传输模型,结合速率方程理论,建立DSCCP超荧光光纤光源数值模型,该模型能够较好地描述泵浦光和信号光演变的物理过程;根据最大总增益等于腔内损耗这一寄生振荡判定条件,建立寄生振荡阈值计算模型;利用数值方法求解建立的超荧光光纤光源速率方程理论模型,研究其输出特性和限制功率提升的因素。理论研究发现:光纤输出端面的光纤反馈是限制功率提升的主要因素;此外,增益光纤长度会影响整个光纤的增益状态,增大光纤长度会导致短波部分的ASE被重吸收,在某一光纤长度下,寄生振荡波长出现由短波1045 nm向1070 nm的大幅转换,而这一光纤长度下的ASE输出功率最大,我们将其定义为最优光纤长度,该最优长度与稀土离子掺杂浓度成反比关系;较大的纤芯包层比有益于抑制寄生振荡的出现,可以一定程度上提升ASE最大输出功率。2.基于DSCCP光纤的高功率超荧光光源实验研究搭建30/250-250μm超荧光光纤光源,输出ASE功率达百瓦量级,验证了于DSCCP光纤在高功率超荧光光源上应用的可行性,并实现了全光纤结构。通过优化斜角切割参数,获得7.5°的倾斜输出端面,镜面区域宽度达到光纤直径的4/5,使得粗糙区域与纤芯距离足够大,保证了纤芯端面光学平整。在此基础上,进一步将超荧光输出功率提升到135 W,斜率效率高达79.8%,前后向光谱带宽(FHWM)分别为34 nm和32.8 nm,一分钟内的功率波动不大于±1.4%。同时,实验研究了超荧光光纤光源输出功率与增益光纤长度的关系,验证了理论上最优增益光纤长度的存在,在光纤长度为7.3 m时,获得了最大功率输出186 W,这是目前为止单级超荧光光纤光源的最高输出功率。
[Abstract]:Superfluorescent fiber source is a kind of optical fiber light source which uses amplified spontaneous emission (ASE) process in rare-earth doped fiber to obtain wide-spectrum output. With the increasing of output power, it has been widely used in different fields. Distributed side-coupled cladding pump (DSCCP) is based on evanescent field coupling technology to realize the distributed coupling of pump power, which is expected to achieve further enhancement of superfluorescence output power. In this paper, a design scheme of superfluorescent light source based on DSCCP fiber is proposed, and a numerical model of superfluorescent light source based on DSCCP fiber is established. The output characteristics and power rise limiting factors are analyzed, and the experimental design is optimized. An all-fiber superfluorescent light source with high power output is obtained. The main work of this paper is as follows: 1. Theoretical research and numerical simulation of superfluorescent light source based on DSCCP fiber A numerical model of DSCCP superfluorescent fiber source is established according to the simplified pump light coupling transmission model of DSCCP fiber and the theory of rate equation. The model can describe the physical process of the evolution of pump light and signal light, and establish a model for calculating the threshold of parasitic oscillation according to the condition that the maximum total gain is equal to the loss in the cavity. The theoretical model of the rate equation of superfluorescent fiber source is solved by numerical method. The output characteristics and the factors limiting the power increase are studied. It is found that the fiber feedback at the output end of the fiber is the main factor limiting the power increase, in addition, the gain fiber length will affect the gain state of the whole fiber, and the increase of the fiber length will lead to the reabsorption of the ASE in the shortwave part. A large conversion of the parasitic oscillation wavelength from 1045 nm to 1070 nm occurs at a certain fiber length, and the output power of the optical fiber is the largest, which is defined as the optimal fiber length. The optimum length is inversely proportional to the doping concentration of rare earth ions, and the larger core-cladding ratio is beneficial to the suppression of parasitic oscillation, and the maximum output power of ASE can be increased to a certain extent by .2. The experimental study of high power superfluorescent light source based on DSCCP fiber is carried out, and the output ASE power is 100 watts. The feasibility of DSCCP fiber applied in high power superfluorescent light source is verified, and the all-fiber structure is realized. By optimizing the angle cutting parameters, an inclined output end face of 7.5 掳is obtained. The width of the mirror area reaches 4 / 5 of the diameter of the fiber, which makes the distance between the rough area and the core large enough to ensure the optical leveling of the core end face. On this basis, the superfluorescence output power is further raised to 135 W, the slope efficiency is as high as 79.8, the forward and backward spectral bandwidth (FHWM) is 34 nm and 32.8 nm, respectively, and the power fluctuation within one minute is less than 卤1.4 nm. At the same time, the relationship between the output power and the gain fiber length of the superfluorescent fiber source is experimentally studied, and the existence of the theoretical optimal gain fiber length is verified. When the fiber length is 7.3 m, The maximum output power is 186 W, which is the highest output power of single stage superfluorescent fiber source so far.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253

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