全光纤再生放大器的研究
文献类型：学位论文
| 作者 | 饶大幸 |
| 学位类别 | 硕士 |
| 答辩日期 | 2013 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 范薇研究员 |
| 关键词 | 前端 光纤放大 再生放大 高稳定性 非线性效应 |
| 其他题名 | Research of All-fiber Regenerative amplifier |
| 中文摘要 | 随着光纤技术的飞速发展，国际上惯性约束核聚变（ICF）激光驱动装置的前端系统逐步走向全光纤化。前端系统作为高功率激光系统的重要组成部分之一，其主要功能是提供具有时间波形控制能力、光谱控制、近场强度控制能力、信噪比控制的高稳定多档脉冲输出。光纤再生放大器结合光纤和再生放大技术可以获得高增益、高信噪比输出，工作在饱和放大状态可以有效提高系统输出稳定性，在ICF前端系统中有良好的应用前景。 本文围绕全光纤再生放大器开展了以下几个方面的研究工作： 1. 概述了惯性约束核聚变的发展及光纤光学在高功率激光驱动装置前端系统的应用，并介绍了光纤再生放大器的国内外发展现状； 2. 介绍光纤放大的相关理论，推导光在光纤中的传输方程，介绍掺镱石英光纤的能级结构和光谱特性，简单介绍了光纤放大器的基本工作原理，并分析了光纤中几种常见的非线性效应； 3. 基于速率方程以单程光纤放大器为基础建立光纤再生放大的理论模型，分别分析了输入功率、泵浦功率及增益纤长度对增益的影响，为实验提供有力的参考依据； 4. 提出全光纤再生放大器的设计方案，并完成搭建，实验分析了再生放大器对几种不同的信号光的放大特性。 1） 对单纵模削波整形3.5 ns脉冲的放大实现增益32dB的饱和放大，信噪比为36dB（与基座相比）。在输出入信号幅度波动15%（RMS）时，输出幅度稳定性为2%（RMS），有效提高了信号稳定性，从理论分析和实验判断限制放大器的因素为受激拉曼散射（SRS）； 2） 对脉冲宽度为250ps宽光谱啁啾脉冲的放大,获得38dB的饱和增益，信噪比为62dB（与连续背底相比），输出波形无明显畸变，说明再生放大器具备宽谱脉冲放大的能力； 3） 对窄线宽长脉冲放大，获得20dB饱和增益，信噪比为60dB（与连续背底相比），方波扭曲(SPD)为2.2，经判断增益受限于受激布里渊散射（SBS）。为提高SBS阈值，引入位相调制单元，获得饱和增益27 dB，能量为1.46 μJ，实验判断了导致输出信号幅频调制效应的原因，并利用偏振控制的手段减弱了幅频调制效应。完成了光纤再生放大器的工程化验证，可以有效的提高系统的输出能量、信噪比及输出稳定性。 5. SRS和SBS是限制光纤再生放大器的主要因素，为提高受激散射阈值，分别对增益光纤的长度进行优化及对2×2端口声光调制器（AOM）的结构进行优化，得出最优增益纤长度为2m，并有效的提高了AOM的开关速度，为光纤放大器的进一步优化提供重要依据。 |
| 英文摘要 | With the rapid development of fiber-based technologies, the front-end system of inertial confinement fusion (ICF) laser driver is developing towards all-fiber system gradually. As one of the most important part of high power laser system, the front-end system provides multiple output pulses of high stability which contain control ability of time waveform, spectrum and near field intensity. The all-fiber regenerative amplifier combined with fiber technology and regenerative amplification technology can obtain a high-gain output with high signal-to-noise ratio. Working in saturation the regenerative amplifier has a high output stability, which can improve the stability of the system output effectively. As result, the all-fiber regenerative amplifier has a good prospect in the front-end system. This paper focuses on the all-fiber regenerative amplifier discussing the research as follows: 1. Outline the development of inertial confinement fusion and applications of fiber optics in the front-end system of high-power laser-driver, and describe the development of fiber regenerative amplifier home and abroad; 2. Introduce the theories of fiber amplification, and derive the propagation equation of light in the fiber, then introduce the energy level structure and spectral characteristics of Yb-doped silica fiber, besides, the basic principle of fiber amplifier is introduced briefly, and some common nonlinear effect in fiber are discussed; 3. Based on the rate equations, model of fiber regenerative amplifier is established driving from single-pass fiber amplifier. Then, relationship of input power, pump power and the length of the gain fiber versus the total gain are analyzed to provide a strong reference for the experiment; 4. Propose the design of all-fiber regenerative amplifier and finish the experimental facility. Analyze the characteristic of a regenerative amplifier with different signals. 1) Amplify the 3.5ns pulse clipped from single longitudinal mode achieving 32 dB saturation gain with signal-to-noise ratio of 36 dB (peak to pedestal). Although the amplitude of the input signal has a fluctuation of 15% RMS, the output fluctuation is less than 2% RMS, which can improve the stability effectively. Then study the stimulated Raman scattering (SRS) which limits the output of amplifier from the theoretical analysis and experimental. 2) Amplify the 250ps chirped pulse with wide spectrum achieving 30dB saturation gain with signal-to-noise ratio of 62 dB (compared with the continuous background). The output waveform is similar with that of input, indicating that the regenerative amplifier has the capacity of amplifying the pulses with wide spectrum. 3) Amplify the 40 ns pulse clipped from single longitudinal mode achieving saturation gain of 20 dB with signal-to-noise ratio of 60 dB (compared with the continuous background). The square pulse distortion (SPD) is 2.2. Further amplification is restricted by stimulated Brillouin scattering (SBS). In order to raise the SBS threshold, the phase modulation unit is introduced. Amplify the pulse after phase modulation obtaining a saturation gain of 27 dB, the energy is 1.46μJ corresponding. Then analyze the reason for amplitude-frequency modulation effects experimentally. And use the polarization controller to weaken the amplitude-frequency modulation effects. 5. The main factor that limits the all-fiber regenerative amplifier are SRS and SBS. In order to increase the stimulated scattering threshold, the length of the gain fiber and the structure of the 2×2 port acousto-optical modulator (AOM) are optimized, respectively. As a result, the most priority gain fiber length is 2m, and the switching speed of the AOM is improved effectively, which provide an important reference for further optimization of the regenerative amplifier. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16755]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 饶大幸. 全光纤再生放大器的研究[D]. 中国科学院上海光学精密机械研究所. 2013. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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