In this paper , by using the method of geometrical optics and the theory of fiber optics mode , we analyzed difference characteristics of double - clad fiber andthe effect of all kinds of dcf ' s inner - cladding structures on1 the absorption efficiency of dcf and its laser 因此在本论文里采用几何光学和纤维光学模式理论的方法分析了不同内包层结构的双包层光纤对光纤激光器性能的影响，建立理论分析模型，并设计了新型内包层结构的双包层光纤。
The new fiber laser , including photonic crystal fiber ( pcf ) laser and multi - core double - clad fiber laser , was analyzed . one of novel structure . dcf laser that will be used into high power output was put forward based on the theoretic analysis 分析了新型光纤激光器(如光子晶体光纤激光器及多纤芯双包层光纤激光器)的基本原理及发展现况，设计了一种新型可实现高功率输出的双包层光纤激光器结构，并从理论分析出发给出其工作原理及制作方法。
2 . considering the energy level structure and the spectrum characteristics of yb3 + ion , we deduce the relationships between laser performances of yb3 + - doped double clad fiber laser and parameters of laser cavity from the steady state rate equations with a new model 2 .讨论了yb3 +离子的能级结构和光谱特性,并从稳态速率方程,结合谐振腔结构特点采用ido kelson和amos hardy的模型,给出了双包层光纤激光器的输出特性与激光器谐振腔结构参数的关系准解析表达式。
High - power yb - doped fiber lasers have caused particular interest as a reliable , efficient and compact , low cost source for a variety of applications in industry , printers , free - space communication , national defense and so on . the dissertation focuses on the yb - doped double - clad fiber lasers , the fiber bragg gratings in double - clad fiber , the fiber lasers based on double - clad fiber grating and pumping methods . the research works in detail are shown as follows : 1 本项研究工作结合国家自然科学重点基金和国家八六三项目,研究内容是对包层泵浦的掺镱光纤器件进行研究,从理论和实验两方面对掺镱双包层光纤激光器、放大器,双包层光纤bragg光栅及其选频的光纤激光器,泵浦耦合方式等进行研究,取得了良好的结果。
The basic operation principle and the recent development was summarized generally , the realization of high power fiber laser and its key techniques were analyzed , which including high power fiber pumping modules > dcf and fiber grating technologies , etc . the advancement with the conception of double - clad fiber makes it possible that fiber laser as a type of device with high - power output 在本论文中，首先概述了光纤激光器的发展历史、最新研究现状及最新发展情况，总结了实现高功率光纤激光器所需要的关键技术，如高功率泵浦模块、双包层光纤及光纤光栅技术等。双包层光纤概念的提出使得光纤激光器作为高功率输出器件成为可能。
High power fiber laser is a novel laser technology that combined of the ld fiber modules and its pumping techniques , double - clad fiber ( dcf ) fabricating technology and fiber grating techniques . fiber laser has a important role of application in many fields . it has come in being a laser industry of several billion usd all over the world , and fiber laser has been called one of the greatest inventions at the beginning of 21st century 高功率光纤激光器是集结了激光二极管光纤模块及其泵浦技术、双包层光纤制作技术及光纤光栅技术与一身的新型激光器技术，在众多领域有着重要的应用前景，国际上已是十几亿美元的产业，被誉为二十一世纪初最伟大的发明之一。
We firstly summarize the development of yb - doped fiber lasers , pumping methods and the applications of high - power fiber lasers . 2 . considering the scattering loss , we deduce the relationships between laser performances of yb - doped double - clad fiber laser and parameters of laser cavity from the steady state rate equations , numerically analysis the changes of laser performances , such as laser power with the parameters of laser cavity , including output mirror reflectivity , optimum length of double clad fiber 研究主要内容包括如下几个方面:一、首先对掺镱光纤及掺镱光纤激光器的发展状况、包层泵浦技术和高功率光纤激光器的应用等进行了综述;二、在前人对高功率双包层光纤激光器的理论基础上,在考虑了光纤散射损耗因子的情况对光纤激光器理论进行了推导,给出了准解析解,进一步完善了理论分析。
But the core and na of ld output fiber is larger than that of double cladding fiber ' s inner cladding , it is important to analyze the ray propagating and focusing . the intensity distribution of multi - mode fiber is analyzed based on our experiments . and the optimum coupling efficiency is discussed between two multi - mode fiber , especially for the condition that core radius and na of output fiber are larger than that of input fiber 接着根据输入输出光纤的纤芯直径和数值孔径的不同，分四种情况分析了两光纤之间的耦合效率，着重分析了第四种情形，给出耦合效率的数值模拟曲线，在数值计算中用到了上面得出的输出光纤端口的光强分布，最后实验验证以上的分析。
We numerically analysis the changes of laser performances , such as laser power , with the parameters of laser cavity , including output mirror reflectivity , optimum length of double clad fiber , the cavity loss and concentration values of the fiber . these results are very important when optimizing the structure of a double - clad fiber laser . the variation of the temperature , stress , refractive index and laser efficiency of a high power double clad fiber laser due to the thermal effects is theoretical analyzed by using thermal conduction equations 由激光器输出特性准解析表达式出发详细分析了掺yb3 +双包层光纤激光器输出功率、泵浦功率、光纤的最优长度等参数与后腔镜对信号光反射率r2 、对泵浦光反射率r3 、双包层光纤掺杂浓度等结构参数的关系,并进行了数值模拟,模拟结果表明,激光器的性能参数受其结构参数的影响很大,为优化设计双包层光纤激光器的结构提供了理论依据。
We calculate the stress fracture limit , critical index limit and melting limit in a high power double clad fiber laser . the results show that the average output power decreases when the temperature is too high . to maintain the pumping efficiency and the output power , some cooling methods should be used when the output power reaches a certain level 给出了热效应对双包层光纤激光器影响的裂解极限、临界折射率极限和熔化极限与光纤结构参数和泵浦功率的表达式,理论分析和数值模拟结果表明对于高功率的双包层光纤激光器温度很高时激光增益下降,在一定的功率水平上需要进行外界的冷却,以保证泵浦激光的效率和高功率的激光输出。
