基于光参量放大的超快多幅成像技术

发布时间：2018-06-21 13:37

本文选题：非共线光参量放大 + 空间分辨率　；参考：《深圳大学》2016年博士论文

【摘要】：光参量放大技术是一种典型的非线性技术。由于其结构简单,可以获得高增益、高质量、宽频带的功率和能量放大,因此在众多场合和领域被广泛应用,其中包括应用于图像信息领域的光参量放大成像。本论文将这种技术拓展应用于瞬态光学成像领域。瞬态光学成像是研究超快变化过程的主要光学探测手段,它广泛地应用于对超快过程的诊断,能够同时获得超快变化过程的时间和空间信息。准确地获取超快过程的时间和空间信息,揭示其动态规律并加以控制利用在物理、化学、生物以及医学等领域都有着重要的应用。涉及到国家的军事、航天、科研、医疗和工业等方方面面的技术进步,具有重要的科学研究价值以及社会和经济价值。目前,随着超短脉冲技术的发展,超短脉冲激光已经被广泛地应用于各类超快过程的成像中并将超快成像的时间分辨率推进到皮秒以及飞秒区域。本学位论文提出了一种基于光参量放大的飞秒级分辨的瞬态成像技术。论文内容包括研究的背景介绍,光参量放大的基本理论介绍,基于光参量放大基本成像特性分析,高增益、高空间分辨的光参量放大成像技术,采用飞秒激光泵浦-探测的非共线光参量放大超快多幅成像技术,基于非共线光参量放大的超快实时多幅成像技术以及总结与展望。其中主要的研究内容可以概括为以下几点:1.从理论上计算分析了如何实现高增益、高空间频率带宽的光参量放大成像系统,包括不同的晶体(β-BBO、LBO、KDP)、晶体厚度、泵浦光强度及其空间分布等方面的因素。讨论分析了光参量放大的成像特性,包括其增益特性、空间频率带宽特性等等。计算结果表明:β-BBO晶体在可见光、近红外的光参量放大中显示了更为优良的增益与带宽特性;薄的晶体不利于高增益的光参量放大,但是可以获得大的空间频率带宽与光谱带宽;强的泵浦光强有利于实现高增益、高频率带宽的光参量放大;均匀的泵浦有助于成像分辨率的提高。这些结果为我们的实验研究提供了理论支撑。2.设计实现了高增益、高空间分辨的非共线光参量放大成像方案的实验。根据成像照明信号光源的不同,实验研究的方案包括两种:一种是采用连续光照明、超短脉冲泵浦的光参量放大成像方案,其特色是结构简单紧凑、照明波长选择自由度高、高强度的飞秒脉冲泵浦提供了高增益、高空间分辨带宽的光参量放大器;另外一种是信号光和泵浦光均为飞秒脉冲激光的光参量放大成像方案。每一种方案又分别设计了type-I和type-II两种相位匹配方式进行实验,并在实验中获得了高增益、高空间分辨的闲频光成像。特别是,我们首次提出了利用非共线的.type-.II相位匹配的.光参量放大.成像成像方案获得高空间分辨的闲频光图像.,通过非共线角的设计,不仅有效地抑制了空间几何拖尾效应引起的图像模糊,而且实现了角度的非临界相位匹配获得了更大的空间频率带宽。在实验中,获得了增益高达104,水平方向上空间分辨率达到20.16 lp/mm、竖直方向上空间分辨率达到25.39lp/mm的闲频光图像,对应的二维空间带宽积高达73000。3.利用飞秒激光泵浦-探测的方法,实验研究了基于非共线光参量放大超快多幅成像装置。实验中分别采用连续光照明、超短脉冲泵浦的光参量放大超快多幅成像以及信号光和泵浦光均采用飞秒脉冲激光的光参量放大超快多幅成像两种成像方案。以飞秒激光脉冲产生的竖直方向上具有周期性空间结构的等离子体光栅(条纹宽度约为24μm)为成像的目标物体,分别获得了时序多幅的闲频光图像,成像的时间分辨率仅取决于位移平台的精度。4.首次提出设计了一种基于非共线光参量放大的超快实时多幅成像装置,该装置可以.实现单次同时获得4.幅时序分幅图像,成像的时间分辨率最高可以达到35fs。该装置的特色是各闲频光脉冲空间分离并为各自面阵CCD记录,从而无需任何空间扫描装置,虽然以高摄影频率成像却无需快速响应的面阵CCD。另外,强泵浦意味着高参量放大增益和宽空间带宽,这使得成像有高空间分辨同时对记录介质(面阵CCD)灵敏度要求也大幅降低。实验中分别研究讨论了采用连续光照明、飞秒脉冲激光泵浦取样与采用啁啾脉冲光作为照明光、飞秒脉冲激光泵浦取样这两种基于非共线光参量放大的超快实时多幅成像装置方案,对具有周期性结构的等离子体光栅(条纹间距约为28μm)的演化过程进行了测量,可一次实验获得4幅闲频光时序图像,实验中分幅的时间最短为133.3fs,对应的摄影频率达到7.5×10~12fps。
[Abstract]:Optical parametric amplification (OPO) is a typical nonlinear technology. Because of its simple structure, it can obtain high gain, high quality, and magnification of power and energy of broadband, so it is widely used in many fields and fields, including optical parametric large imaging in the field of image information. This paper applies this technique to transient state. In the field of optical imaging, transient optical imaging is the main optical detection method for studying ultra fast change process. It is widely used in the diagnosis of super fast process, can obtain time and space information of super fast process, obtain time and space information of super fast process, reveal its dynamic law and control the use of it. There is an important application in the fields of science, chemistry, biology and medicine. It has important scientific research value and social and economic value to the military, space, scientific research, medical and industrial aspects of the country. At present, with the development of ultrashort pulse technology, ultra short pulse laser has been widely used in various fields. In the imaging of super fast process, the time resolution of ultrafast imaging is pushed to picosecond and femtosecond region. This dissertation proposes a femtosecond resolution transient imaging technique based on optical parametric amplification. The paper includes the background of the study, the basic theory of optical parametric amplification, and the basic imaging based on optical parametric amplification. Characteristics analysis, high gain, high spatial resolution optical parametric amplification imaging technology, using femtosecond laser pumping and detecting non collinear optical parametric amplification ultra fast multi amplitude imaging technology, ultra fast real-time multi amplitude imaging technology based on non collinear optical parametric amplification and summary and prospect. The main content of the research can be summarized as follows: 1. from The optical parametric amplification imaging system of high gain and high spatial frequency bandwidth is theoretically calculated and analyzed, including the factors of different crystals (beta -BBO, LBO, KDP), crystal thickness, pump light intensity and spatial distribution. The imaging characteristics of optical parametric amplification are discussed and analyzed, including its gain characteristics, spatial frequency bandwidth characteristics and so on. The results show that the beta -BBO crystal shows better gain and bandwidth characteristics in visible light and near infrared optical parametric amplification. Thin crystals are not conducive to high gain optical parametric amplification, but large spatial frequency bandwidth and spectral bandwidth can be obtained. Strong pump intensity is beneficial to high gain and high frequency bandwidth. Magnification; uniform pumping helps to improve imaging resolution. These results provide a theoretical support for our experimental research on the design and implementation of a high gain, highly spatially resolved non collinear optical parametric amplification imaging scheme. According to the difference of the light source of the imaging lighting, the scheme of the experimental research includes two methods: one is the use of.2.. The optical parametric amplification and imaging scheme of ultra short pulse pumped with light illumination and ultrashort pulse is characterized by simple compact structure, high illumination wavelength selectivity, high gain and high spatial resolution bandwidth of optical parametric amplifier with high spatial resolution bandwidth, and the other is the optical parameter of the signal and pump light for femtosecond pulse laser. For example, each scheme designs two phase matching methods of type-I and type-II respectively. In the experiment, high gain and high spatial resolution are obtained. In particular, we first proposed the use of non collinear.Type-.II phase matching, optical parametric amplification, imaging scheme to obtain high spatial resolution. Through the design of non collinear angle, it not only effectively inhibits the image blurring caused by the spatial geometric trailing effect, but also achieves greater spatial frequency bandwidth with the non critical phase matching of the angle. In the experiment, the gain is as high as 104, the spatial resolution of the horizontal direction is up to 20.16 lp/mm, the vertical direction is above the vertical direction. The free frequency optical image with a resolution of 25.39lp/mm, and the corresponding two-dimensional space bandwidth up to 73000.3. using femtosecond laser pumping detection method, the ultra fast multi amplitude imaging devices based on non collinear optical parametric amplification are experimentally studied. Both the signal light and the pump light are two imaging schemes using the optical parametric amplification of femtosecond laser pulse laser. The plasma grating with periodic spatial structure in the vertical direction of the femtosecond laser pulse (the width of the stripe is about 24 m) is the target object. The time resolution only depends on the precision of the displacement platform..4. first proposed the design of a super fast real-time multi amplitude imaging device based on non collinear optical parametric amplification. The device can achieve 4. sequential amplitude images at the same time at the same time. The highest time resolution of the imaging can reach 35fs., which is characterized by the idle frequency light pulse space. It is separated and recorded for each surface array CCD, thus without any space scanning device, although the high photography frequency imaging does not require a fast response array CCD., the strong pump means high parametric amplification gain and wide space bandwidth, which makes the imaging have high spatial resolution and the sensitivity requirements for the recording medium (array CCD) are also greatly reduced. In the experiment, two kinds of ultra fast real-time multi amplitude imaging devices based on non collinear optical parametric amplification by the continuous light illumination, the femtosecond pulse laser pumping sampling and the chirped pulse light as illuminating light and the femtosecond pulse laser pumped sampling are discussed. The plasma grating with periodic structure is about 28 mu. The evolution process of M is measured. 4 idle frequency light timing images can be obtained in one experiment. The shortest time of the experiment is 133.3fs, and the corresponding frequency is 7.5 x 10~12fps..
【学位授予单位】：深圳大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O439

【参考文献】