单频纳秒脉冲掺镱光纤激光器及放大器的研究

发布时间：2018-07-10 04:13

本文选题：单频 + 电光调制　；参考：《北京工业大学》2015年硕士论文

【摘要】：光纤激光器具有结构简单紧凑、光束质量好、光光转换效率高等优点成为研究最为广泛的激光器之一。单频纳秒脉冲光纤激光器因为具有极窄的光谱线宽,在相干合成、激光雷达、激光测距等领域有着重要的应用。1μm波段的单频纳秒脉冲激光可以倍频产生绿光输出,高能量单频纳秒脉冲绿光可以作为激光雷达的光源,在测量水温、水流速度等应用中能够提供长距离、高精度的测量。所以研究如何获得高能量的单频纳秒脉冲激光输出具有重要的应用价值。本文对单频激光的强度调制以及单频纳秒脉冲光纤激光放大器进行了理论和实验上的研究,主要工作包括以下几个方面:1、简述了单频光纤激光放大器的研究背景和意义,介绍了全光纤单频激光放大器国内外的研究进展,以及单频纳秒脉冲激光放大器在实际中的一些应用。2、从镱离子能级结构出发,在理论上给出了单频掺镱光纤激光放大器的速率方程和边界条件;介绍了激光在光纤中传输容易产生的几种非线性效应,着重讨论了受激拉曼散射(SRS)和受激布里渊散射(SBS)这两种非线性效应;在理论上描述了窄线宽纳秒脉冲光纤激光放大器中的SBS动力学过程,分析了窄线宽纳秒脉冲光纤激光放大器中易产生SBS的根本原因,提出了抑制SBS的几种方法,并讨论了几种方法共同抑制SBS效应的可行性。3、介绍了调Q和调制这两种获得纳秒脉冲激光输出方法的基本原理,阐述了利用任意波形发生器(AWG)和电光调制器(EOM)对连续激光进行强度调制获得脉冲宽度和重复频率可控制的脉冲激光输出的基本原理,并且通过调节AWG和EOM相关参数,得到了与调制信号波形参数一样的稳定脉冲激光输出,为下一步单频纳秒脉冲激光的放大提供了一个很好的种子源。4、介绍了在光纤激光放大器实验中SBS效应的抑制方法,在理论上计算了SBS的阈值,实验上对主放大级采用大模场面积双包层光纤、水冷等方式提高SBS的阈值。对脉冲宽度为10 ns,重复频率分别为10 kHz和5 k Hz的单频脉冲激光进行全光纤MOPA放大,得到了平均输出功率23.24 W、23.12 W,单脉冲能量和峰值功率分别为2.3 mJ、230 kW和4.6 mJ、460 k W稳定的放大脉冲激光输出,并进行了初步的腔外倍频实验。
[Abstract]:Fiber laser has become one of the most widely studied lasers with the advantages of simple and compact structure, good beam quality and high optical conversion efficiency. Single frequency nanosecond pulsed fiber laser has important applications in coherent synthesis, lidar, laser ranging and other fields because of its very narrow spectral linewidth. The single-frequency nanosecond pulse laser at the wavelength of .1 渭 m can double frequency to produce green light output. High-energy single-frequency nanosecond pulsed green light can be used as a light source for lidar. It can provide long distance and high precision measurement in the applications of measuring water temperature and flow velocity. Therefore, the study of how to obtain high energy nanosecond pulse laser output has important application value. In this paper, the intensity modulation of single-frequency laser and the theoretical and experimental research of single-frequency nanosecond pulsed fiber laser amplifier are studied. The main work includes the following aspects: 1. The research background and significance of single-frequency fiber laser amplifier are briefly described. This paper introduces the research progress of all-fiber single-frequency laser amplifier at home and abroad, and some applications of single-frequency nanosecond pulse laser amplifier in practice, starting from ytterbium ion energy level structure. In this paper, the rate equation and boundary conditions of single frequency ytterbium-doped fiber laser amplifier are given theoretically, and some nonlinear effects of laser propagation in optical fiber are introduced. Two nonlinear effects of stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) are discussed, and the dynamic process of SBS in narrow linewidth nanosecond pulsed fiber laser amplifier is described theoretically. The basic causes of SBS in narrow linewidth nanosecond pulsed fiber laser amplifier are analyzed, and several methods to suppress SBS are put forward. The feasibility of several methods to suppress SBS effect is discussed. The basic principles of Q-switched and modulation methods for obtaining nanosecond pulse laser output are introduced. The basic principle of pulse width and repetition rate controlled pulse laser output by using arbitrary waveform generator (AWG) and electro-optic modulator (EOM) for intensity modulation of CW laser is described, and the parameters of AWG and EOM are adjusted. The stable pulse laser output, which is the same as the modulation signal waveform parameter, is obtained, which provides a good seed source for the next step of single-frequency nanosecond pulse laser amplification. The method of SBS suppression in the experiment of fiber laser amplifier is introduced. The threshold value of SBS is calculated theoretically, and the threshold value of SBS is increased experimentally by means of large mode field area double-clad fiber and water cooling. An all-fiber MOPA amplifier is used to amplify single-frequency pulse laser with pulse width of 10 ns and repetition rate of 10 kHz and 5 kHz, respectively. The average output power is 23.24 WN 23.12 W, the single pulse energy and peak power are 2.3 MJ ~ (2 +) 230 kW and 4.6 mg ~ (-1) 460kW, respectively, and stable amplification pulse laser output is obtained, and a preliminary experiment of frequency doubling out of the cavity is carried out.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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