【作者】 黄小东；

【导师】 张小民；

【作者基本信息】 山东大学 ， 光学工程， 2010， 博士

【摘要】 光纤系统具有具有技术先进、功能全、指标高、可编程控制、分束可靠、光纤传输灵活稳定、系统稳定可靠的特点,因此在激光驱动的惯性约束聚变中有很好的应用前景。特别是在用于惯性约束聚变的大型激光装置中,全光纤前端系统作为种子光源,已经发挥了巨大的作用。正弦相位调制脉冲是目前国内外高功率激光装置普遍采用的一种种子源。它一方面能提供一定的带宽抑制大口径光学器件的横向受激布利渊散射；另一方面,它可以提供随时间变化的周期性啁啾以满足束匀滑实验的要求。本文系统的研究了采用该技术路线的高功率激光装置尤其前端光纤系统所遇到的问题,其中包括群速度色散、偏振模色散、增益窄化以及光学器件的弱标准具等对FM-AM效应的影响。此外,新一代的高功率激光装置要求前端输出能量进一步的提高,以减轻后续系统的压力,所以对于光纤放大器的理论研究也是构建前端光纤系统的主要依据。最后,作为一种前瞻性的脉冲整形技术,对于啁啾脉冲堆积方案的理论研究可以作为高功率激光装置新的种子源产生方式的依据。本论文的主要内容：Ⅰ.在脉冲在光纤中传输的理论基础上,分别对群速度色散、偏振模色散、自相位调制、受激布利渊散射等光纤中对脉冲传输产生影响的因素进行了理论分析,并通过实验着重研究了单模光纤中群速度色散、偏振模色散以及保偏光纤输出偏振态的稳定性对相位调制脉冲的影响。Ⅱ.理论分析了现有的光纤放大器速率方程以及宽带光纤放大器模型的不足,在此基础上提出了包含反转粒子数分布、色散以及非线性效应的宽带放大器模型以及计算方法,并对光纤放大器的一些边界条件展开了讨论。在此基础之上,给出了短脉冲光纤放大器中的受激布利渊散射的理论模型,初步开展了相关的实验研究。最后,开展了高功率光纤放大器的相关实验,介绍了高效高功率的全光纤激光系统,并结合理论对实验结果进行了讨论,实验结果与理论模拟吻合较好。Ⅲ.首先介绍了正弦调频脉冲的产生原理与方式,对高功率固体激光装置前端系统采用正弦调频脉冲技术方案后遇到的主要问题FM-AM效应进行了理论分析,并着重正对系统中的波片和增益窄化等问题展开了理论和实验研究。最后,提出了高功率固体激光系统中FM-AM效应的主要补偿手段,并对每个补偿方式进行了理论分析,总结了各补偿方式的优点和不足。Ⅳ.分析了啁啾脉冲堆积的整形方式,对高斯啁啾堆积脉冲的特性进行了理论分析,讨论了色散、自相位调制以及放大等对堆积脉冲影响。实验研究了高斯啁啾堆积脉冲的频谱特性、任意整形能力以及时间调制对高功率激光装置的影响。针对高斯啁啾堆积脉冲的特性,提出了采用超高斯啁啾脉冲作为脉冲堆积中子脉冲的技术路线,分析了超高斯线性啁啾堆积脉冲的时谱特性、传输特性以及放大特性。最后提出了脉冲堆积的其他相关应用。本论文的主要创新点：Ⅰ.对正弦相位调制脉冲在高功率激光装置前端光纤系统中传输遇到的问题进行了系统的讨论,理论和实验研究了群速度色散、偏振模色散对相位调制脉冲波形的影响。Ⅱ.提出了包含反转粒子数分布以及色散、非线性效应的宽带光纤放大器理论模型,该模型能够更加准确的描述高功率光纤放大器,计算过程中没有对放大器增益曲线进行洛伦兹或者高斯近似,而是采用实际的增益分布进行模拟,从实验的结果来看,与该模型吻合较好。并且开展了高效高功率的全光纤激光系统实验,实验结果在国内同条件的系统中处于领先的水平。Ⅲ.针对单纵模光纤放大器实验中观察到的瞬态受激布里渊散射,提出了高功率光纤放大器中瞬态受激布里渊散射(SBS)的理论模型,并对其特性进行了初步的理论研究,实验和理论结果表明,瞬态的SBS会造成单纵模脉冲在光纤放大器中的波形畸变,从而限制了放大器的输出。Ⅳ.初步系统研究了高功率激光装置中FM-AM的效应,尤其对于高功率激光装置中的波片等光学器件的若标准具效应进行了理论和实验研究,结果吻合较好。并针对导致高功率激光装置中FM-AM效应的因素繁多复杂的情况,提出采用液晶空间光调制器进行任意形状强度传递函数和相位传递函数的补偿的可行性。Ⅴ.针对高斯啁啾堆积脉冲存在时间调制的问题,提出了采用超高斯线性啁啾脉冲堆积产生高占空比整形脉冲的技术路线,并进行了相关的理论分析。更多还原

【Abstract】 Optical system has a technologically advanced, full functions, indicators of high, programmable control, splitting reliable, flexible and stable fiber-optic transmission, system stable and reliable characteristics, so it has a good prospect in laser-driven inertial confinement fusion. Particularly for large-scale laser inertial confinement fusion devices, all-fiber front-end system as a seed source, has played a significant role.Sinusoidal phase modulation pulse is generally used as a seed source on high-power laser device at home and abroad. The one hand it can provide some optical bandwidth to suppress the transient stimulated Brillouin scattering in large diameter optics; the other hand, it can provide periodic chirp over time to meet the experimental requirements for beam smoothing. The article systematic studies the problems encountered in high power laser facility using this technical line, particularly in the front-end system, including the group velocity dispersion, polarization mode dispersion, gain narrowing and optical devices with weak etalon effects on the FM-AM effects. In addition, the new generation of high-power laser system required to further improve output energy of the front-end to reduce the pressure on the follow-up system, so the theory of the optical fiber amplifier is the main basis for front-end optical systems. Finally, as a forward-looking pulse shaping techniques, the theoretical study of chirped pulse stacking scheme can provide a new way to produce the seed source for high-power laser facility.The main constents of this paper:Ⅰ. Based on the theory of the pulse transimission in the optical fiber, respectively, the effects of group velocity dispersion, polarization mode dispersion, self phase modulation, stimulated Brillouin scattering on optical pulse propagation were theoretical analyzed, and the effects of group velocity dispersion, polarization mode dispersion and polarization stability of polarization-mataining fiber on frequency modulated pulse were experimentally studied.Ⅱ. First, we theoretically analyzed the deficiency of the existing optical fiber amplifier and broadband fiber amplifier rate equation model, then broadband amplifier model that contains the inversion、dispersion and nonlinear effect, and the calculation method were put forward on this basis. Next, some boundary conditions of the amplifier were discussed. On this basis, the model of stimulated Brillouin scattering in fiber amplifier was proposed, and the corresponding experiment was carried out. Finally, introduced a highly efficient high-power fiber laser systems, and the experimental results were theoretically discussed, the experimental results agree well with the theoretical simulation.Ⅲ. First, introduced the principle of sinusoidal frequency modulation and pulse generation methods, the FM-AM effect encountered in the front-end system of high-power laser facility using sinusoidal frequency pulse technology is theoretically analyzed, and the effect of wave plate、gain narrowing and other issues were theoretically and experimentally studied. Finally, the principal means of compensation to the FM-AM effect were proposed, and each method was theoretically analyzed, then the advantages and disadvantages of each method were summarized.Ⅳ. The shaping method of chirped pulse stacking was studied, and the characteristics of chirped pulse stacking were theoretically analyzed, which contains the effect of the dispersion, self-phase modulation and amplification effect on the stacked pulses. The stacked pulse spectrum、arbitrary shaping ability and the time modulation impact on the high power laser facility were experimentally studied. Then a method of super-Gaussian chirped stacking technique was proposed, and the time domain and frequency domain、transmission and amplification characteristic of the super-Gaussian stacking pulses were analyzed. Finally, the other relevant application was proposed.The main innovation of this paper are as follows:Ⅰ. The problems encounterd during the sinusoidal phase modulation pulse transmission in the front-end system of high power laser facility are systematically discussed, and the effects of the group velocity dispersion, polarization mode dispersion on the phase modulation of pulse waveform were theoretically and experimentally studied.Ⅱ. The broadband fiber amplifier model was proposed, which contains inversion distribution、dispersion and nonlinear effect, and the model can more accurately describe the high-power fiber amplifier. There was no approximation for the gain function, and the actual gain distribution was used in simulation, and the model has a good agreement with the experiment results. Then launched a highly efficient high-power fiber laser system, and experimental results with the same conditions in the domestic is in the leading level.Ⅲ. For the transient stimulated Brillouin scattering observed in single-frequency fiber amplifier experiment, the model for transient stimulated Brillouin scattering (SBS) of high-power fiber amplifier was proposed. Then the model and its characteristics were preliminary theoretical study, experimental and theoretical results show that the transient SBS will cause a single-frequency pulse waveform distortion in the optical fiber amplifier, and limiting the amplifier output.Ⅳ. The FM-AM effect in high power laser facility was preliminary systematic studied, especially for the weak etalon effect of waveplate and other optics in high-power laser facility, experiment and theoritcal study were carried out, and theoretical and experimental research results agree well. Beacause of many complicated factors could result in FM-AM effect in high power laser facility, the method of liquid crystal spatial light modulator used to compensate arbitrary amplitude and phase transmission function was proposed.Ⅴ. For the time modulation existed in the chirped Gaussian stacked pulse, the technology of super-Gaussian linearly chirped pulse stacking was proposed, and the corresponding theoretical study was carried out.更多还原