基于谱相干的飞秒脉冲电场重构系统的设计与实现

发布时间：2018-01-30 04:05

本文关键词： 飞秒激光频率分辨相位级联矩形滤波高斯滤波　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：从20世纪60年代梅曼发明红宝石激光器开始,人们一直致力于激光技术的改进,从连续激光到调Q激光再到基于锁模技术的皮秒、飞秒激光[1],激光的脉冲宽度变得越来越窄,峰值功率越来越高,其在科学实验及生产中的应用也变得越来越广.作为一个基础性的工作,对于激光脉冲尤其是皮秒、飞秒激光,如何测量其脉冲宽度及相位成为激光应用首先要解决的问题。对于纳纱量级的激光脉冲,仅用示波器就可以测定其脉冲的宽度,而对于皮秒或飞秒量级的脉冲,电子的示波器由于响应速度不够快,无法测量其脉冲宽度,条纹相机或是改进的条纹相机虽然可以测量其脉宽,但是条纹相机本身的价格十分昂贵,无法普及.事实上,科学家先后提出三种更为常见的超短脉冲脉宽及相位测量方法:自相关法(AC)、频率分辨光学开关法(FROG)、基于谱相干的脉冲电场重构法(SPIDER).本文所采用的方法是基于谱相干的脉冲电场重构法.利用频率上具有一定侧切量的两束脉冲进行干涉,对干涉谱中所包含的相位信息通过傅里叶变换及相位积分或级联的方法对相位进行重构,在此基础上,再结合原始脉冲频谱对脉冲在脉冲的脉宽进行重构.本文主要的研究内容如下:研究了飞秒激光脉冲线性自相关、强度自相关及谱相干的联系与区别,初步论证了谱相干技术应用于飞秒激光脉冲脉宽及相位测量中的可行性,完整给出了相位级联重构法的原理及优化方法.研究了侧切量的引入对于谱相干干涉谱的影响,采用数值模拟的方式定量描述了侧切量对于时域干涉信息分布的影响,针对时域干涉信息分布图,给出了合理的矩形及高斯滤波函数选取方法.讨论了BBO晶体不同类型的相位匹配对于侧切干涉谱及非侧切干涉谱匹配带宽的影响,确定了BBO晶体匹配类型及厚度等参数,针对实验对展宽脉冲脉宽的要求,计算并确定了光栅对的参数.研究了二次脉宽及相位重构的可行性,通过比对分析,得出关于二次脉宽及相位重构法的一般性结论.讨论了相位重构过程中相位解缠绕与侧切非侧切干涉相位信息整合先后顺序对于相位重构的影响.数值模拟表明,相位解缠绕与侧切非侧切干涉谱相位信息整合先后顺序对于相位的重构结果有较大的影响,而基于重构的相对所得到的相位余弦随频率变化图是一致的.提出了对SPIDER的改进方案,对近十年来以减少测量误差、提高测量效率为目的的实验方案进行简单的介绍.本文基于自主搭建的SPIDER实验装置,对本实验室中现有飞秒激光进行脉冲宽度及相位的测量,通过光谱的采集及Labview程序处理,重构了得到39的脉冲宽度及相对相位随频率变化曲线,所重构的相对相位与实际相符,而脉宽则与实验室中自相仪所测量得到的37.38的实验结果符合得较好.
[Abstract]:Since the invention of ruby laser in 1960s, people have been devoted to the improvement of laser technology, from continuous laser to Q-switched laser to picosecond, femtosecond laser based on mode-locked technology. [1. The pulse width of laser becomes narrower and the peak power becomes higher and higher. As a basic work, laser pulse, especially picosecond, becomes more and more widely used in scientific experiments and production. Femtosecond laser, how to measure its pulse width and phase becomes the first problem to be solved in laser application. For nanosecond laser pulse, the pulse width can be measured only by oscilloscope. For picosecond or femtosecond pulse, the electronic oscilloscope can not measure the pulse width because the response speed is not fast enough. The fringe camera or the improved stripe camera can measure the pulse width. In fact, scientists have proposed three more common methods for measuring the pulse width and phase of ultrashort pulses: the autocorrelation method. Frequency resolved optical switch (FROG). Spectral coherence based pulsed electric field reconstruction method is used in this paper, which is based on spectral coherent pulse electric field reconstruction method. Two pulses with certain side tangent are used to interfere. The phase information contained in the interference spectrum is reconstructed by Fourier transform and phase integration or concatenation. The main contents of this paper are as follows: the relationship and difference of linear autocorrelation, intensity autocorrelation and spectral coherence of femtosecond laser pulses are studied. The feasibility of spectral coherence technique in pulse width and phase measurement of femtosecond laser pulses is preliminarily demonstrated. The principle and optimization method of phase concatenation reconstruction are presented, and the influence of side tangent on spectral coherent interference spectrum is studied. The influence of side tangent on time domain interference information distribution is quantitatively described by numerical simulation, aiming at the time domain interference information distribution map. A reasonable selection method of rectangular and Gao Si filtering functions is given, and the influence of different types of phase matching in BBO crystal on the bandwidth of side-cut interference spectrum and non-side-cut interference spectrum matching is discussed. The matching type and thickness of BBO crystal are determined. The parameters of grating pair are calculated and determined according to the requirement of broadening pulse width. The feasibility of secondary pulse width and phase reconstruction is studied. Through comparative analysis. The general conclusion about the method of quadratic pulse width and phase reconstruction is obtained, and the influence of the sequence of phase information integration of phase unwinding and non-side tangent interference on phase reconstruction is discussed. The numerical simulation shows that the phase reconstruction is affected by the sequence of phase unwinding and non-side tangent interference. . The sequence of phase information integration between phase unwinding and non-side tangent interference spectrum has great influence on the phase reconstruction results. The relative phase cosine based on the reconstruction is consistent with the frequency change diagram. An improved scheme for SPIDER is proposed to reduce the measurement error in the last ten years. Based on the self-built SPIDER experimental device, the pulse width and phase of femtosecond laser in our laboratory are measured. Through spectrum acquisition and Labview program processing, the pulse width and relative phase curves of 39 with frequency are reconstructed, and the reconstructed relative phase is in accordance with the actual situation. The pulse width is in good agreement with the experimental results of 37.38 measured by the self-phase analyzer in the laboratory.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN24

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