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chi20191129上海光机所刘诚557644In final optics assemblies (FOAs) of high power laser facility, the laser beam includes the fundamental frequency (1053nm), 2nd (526.5 nm) and 3rd (351 nm) harmonic frequencies after the frequency converter. The energy and quality of the converted 3rd harmonic laser beam which have a dominant effect on the performance of the laser facility will be affected by the quality of the fundamental laser beam, the optical elements in frequency conversion system and the experimental environment. If the wave front of fundamental, second and third harmonic fields can be measured simultaneously, not only the distribution of all these three laser beams but also properties including frequency conversion efficiency, optical element quality can be analyzed, which heavily affect the practical operation performance of physical experiments. However, because of the very limited inner space of the laser drivers and the vacuum environment, it was previously impossible to simultaneously measure all these three laser beams using conventional techniques. Direct imaging based on precision imaging system and Hartmann sensor are two main conventional methods to measure the intensity and phase information respectively. However, the imaging system inevitably has aberrations and defects while the resolution of Hartmann sensor is limited by the micro lens array and not suitable for large phase distortion. To solve these problems, coherent diffraction imaging (CDI) is applied to measure the laser beam quality in high power laser facility. CDI is a phase retrieval technique that employs iterative algorithms to simultaneously reconstruct the amplitude and phase information from the recorded diffraction patterns with simple structure and high spatial resolution. Ptychographic iterative engine (PIE) and coherent modulation imaging (CMI) are two CDI methods used in high power laser facility. PIE is commonly used for offline measurement of large-scale optical elements in laser driver, but it is not suitable for measuring pulse lasers due to the scanning mode. However, data redundancy caused by scanning also makes it available for multi-mode reconstruction. CMI is a single-shot CDI technique which has a fast convergence speed with only one diffraction pattern. Its simple structure and low environmental stability requirements make it suitable for wave front measurement of pulse lasers but it cannot be used for multi-mode reconstruction. Therefore, this thesis focus on the method that can reconstruct multi-mode with only one diffraction pattern. The main contents of this thesis are as follows: (1) A novel multi-mode CMI algorithm was proposed by combining the multi-mode theory with CMI method. Simulation and experiment demonstrated the feasibility of multi-mode PIE and color imaging was realized by using three different light sources. Error analysis of CMI was also studied, which was the basis of multi-mode CMI. (2) A dual-wavelength CMI method based on single step random phase plate was proposed. The feasibility of this proposed method was experimentally verified with fundamental and third harmonic frequency. Measurement accuracy and main influencing factors of this method were analyzed. The two main factors were the random phase plate and the laser beam energy ratio and experimental results showed that measurement accuracy can reach 1/5λ for both laser beams. The method that utilized two detectors was also studied and verified to improve the measurement accuracy. (3) A three-wavelength CMI method based on double-step phase plate was proposed. To solve the problem of measuring fundamental, second and third harmonic in high power laser driver, a new double-step phase plate was designed and calibrated that all these three wavelengths can be fully diffracted. The reconstruction algorithm of three-wavelength CMI was completed and simulation analysis and experimental verification were performed. Also, a graphical user interface software for simulation and experimental algorithm was programmed to make analysis easier. (4) Based on the principle of extended measurement range by dual-wavelength and mutli-mode CMI method, an unwrapping optical component measurement method was proposed. The algorithm design of this method was completed while the feasibility of this method was verified numerically and experimentally. Since no-interference coaxial optical path was adopted to realize phase measurement and phase unwrapping with single shot exposure, this proposed method has high advantages of simple optical setup, convenient operation, less requirement on environmental stability and quite satisfying accuracy over conventional interferometry based techniques.2020atalunwen2218155558397Coherent diffracition imaging;Phase retrieval;Multi-mode reconstruction; Iterative algorithms.Research on multi-wavelength laser beam measurement based on muli-mode reconstruction基于多模态重建的复合光场测量技术研究在高功率激光驱动器靶场终端系统中,基频光(1053nm)经过频率转换系统后,会同时存在着基频(1053nm)、倍频(526.5nm)和三倍频(351nm)三种波长的光。入射基频光的光束质量,频率转换系统中光学元件的状态以及空间环境等都会影响最终打靶的三倍频光束质量,从而影响到装置性能和物理实验结果。如果能够同时测得三种波长光的光束质量,一方面可以对三种波长光的分布状态有直观了解,另一方面可对终端光学元件的状态以及频率转换等相关问题进行深层次的分析。然而驱动器的靶室空间十分有限并且又处在一个完全真空的环境中,考虑到传统方法测量光束质量的技术复杂性,目前这种测量一直没有进行。 驱动器中传统方法对光束质量强度的检测一般采用基于精密成像系统直接成像的方式进行,对于波前相位的测量采用哈特曼传感器,强度与相位无法同时测量。除此之外,成像系统不可避免地存在像差及缺陷,而哈特曼传感器的空间分辨率较低,并且对于较大的波前畸变无法测量。针对上述问题,基于相干衍射成像(Coherent Diffraction Imaging, CDI)的新型测量手段在驱动器中得以应用。相干衍射成像是一种利用探测器记录到的衍射斑强度信息结合相应迭代算法进行波前重建的技术,其具有光路结构简单、理论上精度能够达到衍射极限等优势,并且可同时测量得到强度与相位信息,从而实现单光路多参数的测量。目前CDI在高功率激光驱动器中的应用主要利用PIE(Ptychographic Iterative Engine)方法和相干调制成像CMI(Coherent Modulation Imaging)方法来进行测量。PIE是一种基于多光斑扫描成像的方法,在驱动器中多用于对大口径特殊光学元件的离线检测,但其扫描的方式不适用于对驱动器中脉冲光束的测量,然而扫描带来的数据冗余性可以实现多模态的重建;CMI只需要记录一幅衍射斑依然可以保证较快的收敛速度,结构简单,对环境稳定性要求较低,特别适用于高功率激光驱动器中脉冲光束的波前测量和诊断,但其无法进行多模态的重建。因此,本论文围绕单次测量下多模态的同时重建,对相关问题进行了研究,主要内容为: (1)将PIE多模态重建的思想与CMI方法结合,提出了单次曝光多模态相位恢复算法。对系统中存在多个波长照明光的多模态PIE进行了模拟与实验研究,利用红绿蓝三种波长的照明光以及多状态PIE算法实现了彩色成像。建立了CMI误差分析模型,为多模态CMI的提出奠定了基础。 (2)提出了基于单台阶相位板的双波长CMI方法,针对高功率激光驱动器中的测量需求,验证了该方法对基频三倍频同时测量的可行性。分析了此技术的测量精度和主要影响因素,确定了影响此技术测量精度的主要两个因素:相位板分布及复合光束能量比。测量结果表明,基频与三倍频光分别达到了1/5波长的测量精度。利用双探测器法进行了测量精度提升技术研究及精度提升能力验证,实验结果表明,双探测器法可以使得能量较低一方测量精度得到显著提升。 (3)提出了基于双台阶相位板的三波长CMI测量方法。针对高功率激光驱动器中的基频倍频和三倍频光,设计与标定了新型的双台阶相位板,其可对三种波长的光进行充分衍射从而实现快速收敛;完成了三波长CMI的重建算法,进行了三波长同时重建的模拟分析与实验验证,并对模拟及实验重建算法封装集成图形用户界面程序。 (4)利用多模态CMI重建算法和双波长合成可增大测量范围的原理,提出了基于双波长CMI的非解包裹光学元件测量方法。完成了新型双波长非解包裹光学元件测量的算法设计,模拟与实验验证了该方法的可行性。相比于双波长干涉法,其光路复杂性和技术难度显著降低,对环境稳定性要求低,抗干扰能力强;同时,作为一种单次曝光测量技术,其数据采集速度更快、操作更方便。相干衍射成像;相位恢复测量;多模态重建;迭代算法中国科学院上海光学精密机械研究所董学光学工程博士
中文题目: 基于多模态重建的复合光场测量技术研究
外文题目: Research on multi-wavelength laser beam measurement based on muli-mode reconstruction
作者: 董学
导师姓名: 刘诚
学位授予机构: 中国科学院上海光学精密机械研究所
答辩时间: 20191129
中文关键词:
相干衍射成像;相位恢复测量;多模态重建;迭代算法
英文关键词:
Coherent diffracition imaging;Phase retrieval;Multi-mode reconstruction; Iterative algorithms.
中文摘要:
英文摘要:
文献类型:学位论文
学位级别: 博士
正文语种: chi
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