【作者】 张志强；

【导师】 沈树群； 任建华；

【作者基本信息】 北京邮电大学 ， 光学工程， 2013， 博士

【摘要】 随着各种新型光纤元件的出现,高功率光纤激光器的制造技术日趋成熟,其相关产品也更加深入地进入到工业、军事、医疗器械等领域。正是由于高功率光纤激光器所体现出的体积小、转换效率高、能量更集中等相对于其他高功率激光器的优势所在,决定了其在制造及科研方面受到的关注越来越多。本文的主要研究内容及创新如下：1.利用线偏振模标量法研究光纤耦合过程,根据光纤特征参数U、W,计算不同模式的耦合系数,再结合光纤功率分布函数,研究光功率在光纤内的传递。提出一种计算多模光纤耦合的数值分析方法,可根据光纤参数计算耦合效率及光纤耦合长度,并指出影响光纤耦合的主要因素。2.经过对双包层增益光纤的吸收特性公式的理论推导与数值仿真,在分析了光纤掺杂浓度、模场直径、光纤损耗等因素对光纤增益的影响基础上,设计Yb双包层光纤激光器的结构。利用分析结果合理选择增益光纤,确定增益光纤长度、纤芯半径及泵浦吸收率等参数。同时,选择相互匹配的光纤器件,完成系统结构初步设计3.根据Yb光纤吸收谱特性,在泵浦激光器工作波长976nm附近进行理论分析,研究FBG的反射特性及WDM分光特性,数值模拟光栅长度及光栅调谐量对光栅性能产生的影响。利用短半波振荡周期WDM设计的全光纤波长检测器,检测泵浦激光器输出波长,根据分析结果,设计泵浦激光器工作波长控制系统,以提高光纤激光器系统泵浦效率。通过泵浦激光器控制系统,提高光光转换效率。4.研究组成光纤激光器系统的主要光学元件,如Yb光纤、泵浦激光器、合束器等元件的原理及工作特性,根据实验目的及总体目标,设计合理的光纤激光器结构。采用种子源脉冲驱动输出,经过两级放大的MOPA结构,完成915nm泵浦实验及理论验证；采用一级声光调制产生脉冲激光,二级放大的MOPA,完成样机开发。检测915nm泵浦光纤激光器及976nm泵浦光纤激光器各项运行指标：光光转换效率、脉冲形状、线宽等。5.完成20W脉冲输出光纤激光器样机开发,选定以976nm泵浦实现脉冲激光输出的系统结构,结合泵浦激光器控制优化设计方案,严格控制泵浦工作波长,提高泵浦效率。系统重复频率可以调整,平均功率稳定,单脉冲能量高,实现了免维护运行。更多还原

【Abstract】 With the emergence of various new kind of optical fiber element,他the technology of high power fiber laser producing gets to mature gradually, its related products also get into the fields of industry, military, medical equipment, etc more deeply. Because of the small volume, high conversion efficiency, more centralized energy compared to other high power laser, fiber laser draws more and more attentions from the manufacture and scientific research department. The main research contents and innovation are as follows:1. Using scalar method of linear polarization mode, study fiber coupling process, according to the optical fiber characteristic parameters U, W, calculate coupling coefficient of different fiber modes, and then combined with optical fiber power distribution function, the optical power transmission in fiber is studied. This paper carries out a calculation method of multimode optical fiber coupling numerical analysis, according to fiber parameter, calculate coupling efficiency and fiber coupling length while the main factors influencng fiber coupling is pointed out.2. After theoretical deducing and numerical simulation of absorption characteristic formula of double cladding fiber, based on the analysis of the optical fiber doping concentration, mode field diameter, fiber loss, etc, the factors influence the optical fiber gain, the structure of double cladding Yb fiber laser is designed. Use the analysis result to choose reasonable gain fiber, determine the fiber length, core diameter and absorption rate, etc. At the same time, choose matching fiber components, complete preliminary design of system structure.3. According to Yb fiber absorption spectrum characteristics, carry out the theoretical analysis near the wavelength of976nm in the pump laser, the FBG reflection characteristics and WDM spectral characteristics are studied, simulate the effects of grating length and grating tuning amount to its performance. According to the results of analysis, design pump laser work wavelength control system to improve fiber laser pump efficiency. Designthe full optical fiber wavelength detector with the use of WDM with short half wave oscillation cycle, detect pump laser output wavelength, on this basis, design a kind of pump laser control structure, in order to improve optical conversion efficiency.4. Study the principle and working characteristic of main optical components of fiber laser system, such as Yb fiber, pump laser, combiner, according to experimental purpose and total target, design the fiber laser structure. Apply the MOPA structure with seed source of pulse driving and two level amplifier, finish experimental and theoretical verification in915nm pumping. Complete prototype development with the MOPA strcture that first level of pulse laser using AOM, second amplified level. Test various operation indexs of915nm pumped fiber laser and976nm pumped fiber laser, optical conversion efficiency, pulse shape, the line width and so on.5. Complete the prototype development of20W fiber laser with pulse output, select the structure of pulse output with976nm pump, combined with optimizing design of pump laser control, control the pump wavelength and improve the pump efficiency. System repetition frequency can be adjusted, average power is stable, single pulse energy is high and the free maintenance operation is achieved.更多还原