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题名	光纤在三倍频脉冲激光参数测量中应用研究及三倍频参数诊断实现
作者	何荣斌
文献子类	硕士
导师	朱宝强
关键词	高功率激光 high power laser 紫外脉冲 ultraviolet pulse 紫外光纤 ultraviolet fiber 传输特性 transmission characteristics 激光参数诊断 laser parameter diagnosis
其他题名	Application Research of Fiber in Measurement of Third-harmonic Pulse Laser Parameters and Realization of Third-harmonic Parameters Diagnosis
英文摘要	以高功率激光驱动的惯性约束核聚变（ICF）是实现可控核聚变的重要技术手段之一。随着ICF研究的深入激光点火要求驱动器输出功率不断提高。为了得到更高输出激光功率一是在同样规模下提高激光通量，二是增加激光驱动器的规模和路数。短波长激光能大幅提高靶对激光的吸收效率，实现三倍频参数精密诊断是研究驱动器整体和材料的负载能力的前提条件；光纤以其易集成技术优势已很好应用于高功率激光驱动器基频激光的参数测量。本文目标针对高通量、多数路的三倍频脉冲激光参数精密诊断的需求，一是研究利用光纤传输三倍频测量以期降低系统测量成本, 二是实现三倍频近场分布精密测量为研究损伤奠定基础。 三倍频时间波形反映激光束通过谐波转换为三倍频激光进入靶室进行物理实验激光时间特性，是衡量高功率激光装置综合性能的一项重要参数指标。采用光纤作为传输介质结合时分复用并束测量方法可以有效减少示波器、快响应光电探测器等设备的使用，降低测量系统运行成本。本文第一部分主要研究内容是理论分析和实验研究紫外光纤的三倍频脉冲传输特性及保真传输能力。在充分了解光纤的基本特性以及光纤耦合的原理基础上，分析了影响耦合系统效率的诸多因素，设计了满足实验要求的高效耦合光学系统；同时理论分析了色散效应和非线性效应对激光脉冲在光纤中传输的影响，模拟了不同类型的脉冲波形经过光纤传输后的变化；实验测量光纤芯径和长度对激光脉冲的影响，研究多模光纤和单模光纤的保真阈值，研究结果表明，对于长50米、模场直径 的多模光纤，紫外纳秒激光脉冲功率小于250W时，输出脉冲时间波形基本不变，保真传输。 为实现三倍频参数精密测量，课题组于2015年研制完成驱动器升级装置三倍频精密诊断系统（PDS），实现驱动器升级装置第二路的半输出条件下的三倍频近远场的初步测量。论文第二部分是在2015年实验基础上利用驱动器升级三倍频精密诊断系统对类NIF激光单路驱动器输出的2J/cm2以上通量的三倍频脉冲实现空间及时间参数精密诊断。实验获得全口径低分辨率三倍频近场数据，分析结果显示，近场通量对比度约为0.35，调制度约为2.48，较基频近场有较大程度的恶化。通过局部区域高分辨率近场测量数据发现楔形透镜透射波前引入周期约1mm，深度7nm的相位型周期结构。理论分析表明，对含位相调制的三倍频激光束，通过毫米级周期、7nm幅度起伏结构的元件，将在元件后特定位置引起三倍频激光近场调制近2倍增强（与基频近场相比）。通过实现三倍频参数诊断为研究损伤机制提供可靠数据，对装置高通量运行状态下的后续改进具有重要指导意义。; The inertial confinement fusion (ICF) driven by high power laser is one of the important technical means to realize controlled nuclear fusion. With the deepening of ICF research, laser ignition requires the driver output power to increase continuously. There are two ways to get higher output laser power. The first way is to increase the laser flux in the same size. The second way is to increase the size and number of laser drivers. Short-wavelength laser can greatly improve the efficiency of the target to absorb the laser. Achieving the precision diagnostic of third-harmonic laser parameters is the prerequisite to study the whole driver and the material load capacity; With its easy integration technology advantages, fiber have been well applied to fundamental frequency laser parameter measurement in high power laser driver. This paper aims to study the demand of the high-flux, multi-channel third-harmonic pulse laser parameters precise diagnosis. Firstly, use of fiber as a transmission medium to measure third-harmonic laser parameters，which reduce the system measurement costs. Secondly, precision measurements of third-harmonic near-field distribution is achieved, which lays the foundation for damage study. The third-harmonic waveform reflects the laser beam temporal characteristics through the harmonic conversion to triple frequency into the target chamber for physical experimental. That is an important parameter of high power laser devicer performance. The use of fiber as a transmission medium combined with time division multiplexing measurement method can effectively reduce the use of oscilloscopes, fast response photoelectric tubes and reduces the operating costs of the measurement system. In the first part of this paper, the main research contents are theoretical analysis and experimental study of the third harmonic pulse transmission characteristics and fidelity transmission capacity of ultraviolet fiber. Based on the understanding of the basic characteristics of fiber and the principle of fiber coupling, the factors influencing the efficiency of coupling system are analyzed, and the efficient coupling optical system satisfying the experimental requirement is designed. At the same time, the influence of dispersion effect and nonlinear effect on the transmission of laser pulse in fiber is analyzed theoretically. The changes of different types of pulse waveforms after fiber transmission are simulated. The effect of fiber diameter and length on the laser pulse is measured. The fidelity threshold of multimode fiber and single mode fiber is studied. The results show that for 50 meters, the mode field diameter of the multi-mode fiber, when UV nanosecond laser pulse power is less than 250W, the output pulse time waveform is basically unchanged, to maintain distortionless transmission. In order to achieve the third-harmonic laser parameters precision measurement, the research group successfully developed the tripled frequency precision diagnostic system (PDS) for the driver upgrade device in 2015, and achieved the initial measurement of the third-harmonic near field and far field distribution under the semi-output conditions of the second upgrade devicer. Based on the experiment in 2015, the space and time parameters precision diagnosis of the third-harmonic pulse is achieved by PDS. The pulse is generated from a class NIF laser single driver with a flux above 2J / cm2. The experimental results show the full-aperture low-resolution third-harmonic field data. The near field flux contrast is about 0.35, the modulation degree is about 2.48. And the near-field distribution has a great degree of deterioration compared with the fundamental frequency. Through the analyze of local area high-resolution near-field measurement data, a phase-type periodic structure with a period of about 1mm and a depth of 7nm introduced by the wedge-shaped lens transmission wave is found. The theoretical analysis shows that for the third-harmonic beam of phase modulation, through the millimeter period, 7nm amplitude of the structure of the components, will be near-field modulation nearly 2 times enhanced at the specific position after the components (compared to the fundamental frequency near-field distribution). Implementing the third-harmonic laser parameters diagnosis provides reliable data for the study of damage mechanism, which is of great significance to the follow-up improvement of the devicer's high-flux operation.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31000]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	何荣斌. 光纤在三倍频脉冲激光参数测量中应用研究及三倍频参数诊断实现[D].

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