Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
Not a member yet
13355 research outputs found
Sort by
Study of channel formation and relativistic ultra-short laser pulse propagation in helium plasma
No full textNational Natural Science Foundation of China [11425418, 11405244, 61221064]; Natural Science Foundation of Shanghai [14ZR1444800]In this study, plasma channel formation in pure He plasma (ionization electron density 0.01-0.1n(c)) interacting with ultra-short relativistic laser pulses (50 fs, >10(19) W cm(-2)) was observed and analyzed. By appropriately selecting the laser pulse and gas backing pressure of the gas jet, a clear density channel longer than 300 mu m and wider than 25 mu m was achieved in less than 1.5 ps following the passage of the laser pulse, with a radial electron density gradient of similar to 10(23) cm(-4) at the channel walls. Numerical simulations for studying the affects of the plasma density, kinetic motion of electrons and ions, and nonlinear laser propagation on the plasma channel formation were carried out, which reproduced the experimental features. These density channels were mainly driven by the radial expulsion of plasma ions, with strong continuous laser self-focusing acting to improve the channeling efficiency. These channels can guide the propagation of ultra-intense laser pulses and supply several advanced applications in high-energy physics, including fast-ignition inertial confinement fusion, plasma-based particle accelerations, and sources of radiation
阿秒科学前沿开拓与强场量子相干控制研究
No full text该研究产生更短脉宽、更高光子能量与更高亮度的阿秒相干光源以及原子分子中阿秒电子波包的探测和控制,预期目标主要包括:(1)实现亚飞秒时间尺度和原子级空间尺度内实时观测和控制电子动力学行为;(2)在多电子弛豫过程中,电子重排、电子-电子碰撞动力学等多电子复杂动力学研究中取得若干突破;(3)揭示有重要意义的化学反应的电子动力学物理本质。探索阿秒脉冲作用下物质的电子动力学新规律及其应用。开展中红外激光与气体介质相互作用产生高次谐波的实验和理论研究,采用双色场方法获得高次谐波连续谱,为进一步将阿秒脉冲宽度测量和光
Light emission enhancement based on surface plasmon resonance in zinc oxide/silver film on digital video disk template
No full textNational Science Foundation of China [21403014]; Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions [PXM2014_014223_000029]; General Program of Science and Technology Development Project of Beijing Municipal CommThe photoluminescence signals of zinc oxide/silver films based on digital video disk template were carried out compared with that of the planar mode. The spectra that on silicon showed a strong bandgap emission around 378 nm and a defect related emission band centered at similar to 470 nm. After adding digital video disk template, it resulted in an increased signal of both the ultraviolet and the visible region, but the ultraviolet emission enhancement was notable. That the enhancement of band edge emission resulted from surface plasmon resonance coupling between silver and zinc oxide was discussed in detail
Investigation of Laser Three Dimensional Ghost Imaging in Motion Scenes
No full text强度关联成像是一种利用热光场辐照目标，由一个无空间分辨能力的单像素探测器获取目标返回信号的涨落信息，通过涨落信息与探测热光场之间的二阶关联运算获取目标图像信息的非局域成像方法。这种新型的成像方式具有分辨率高、探测距离远、系统结构简单等优势，因此强度关联成像从诞生之日起便得到了广泛关注，尤其是在遥感成像领域的开发利用更是取得了显著进展。然而，强度关联成像属于一种凝视成像技术，一个目标场景的成像需要经过若干次探测采样才能完成，长时间的曝光不但会引起运动模糊，而且会加剧环境变化和系统震动等不确定因素的影响。因此相对运动环境中的成像能力是强度关联成像在发展应用过程中的一个核心问题，只有实现了大幅度的相对运动场景下的高质量成像，才能真正使这项新技术走入实际应用的视线。本论文对运动场景下的强度关联成像进行了系统研究，主要从技术方案和成像特点等方面对动态关联成像的关键技术进行了理论研究和实验验证。并根据遥感应用中的需求指标设计加工了一套基于汽车运动平台的激光三维强度关联成像实验样机。论文内容安排如下： 第1章，首先从激光三维成像雷达的角度介绍了激光三维强度关联成像的发展背景和研究现状。通过对目前各类激光成像雷达技术的概述总结，进一步明确了强度关联成像在遥感领域的优势及问题。 第2章，首先详细介绍了静态激光三维强度关联成像系统的基本原理和实施方案；其次对运动场景下强度关联成像的各项关键技术进行了系统研究和方案验证，其中主要包括不同视场下的动态关联成像方案，为实现快速成像而开展的高重频和多点接收研究，以及为克服快速成像导致的脉冲能量降低而开发的光子计数关联成像。明确了各项技术的特点和问题，为运动平台关联成像实验样机的研制提供了技术基础。 第3章，详细介绍了基于汽车运动平台的强度关联成像实验样机设计和加工工作。从总体结构、静态模块和跟踪模块三个方面分别介绍了样机各个部分的光机结构、电控系统和核心器件。 第4章，对运动场景下强度关联成像的特点和车载实验样机在设计加工过程中遇到的问题进行了概括总结。结合目前强度关联成像的发展状况对以后的研究方向和研究重点做了主观方面的规划和展望。Ghost imaging is a non-local imaging method that utilizes thermal light for illuminating and detects the fluctuation of the reflected signals with a single-pixel detector, objects’ information can be reconstructed by second-order intensity correlation between the detected fluctuation information and the illumination information. This unique imaging method has many advantages of high-resolution, distant detection and simple mechanism, so it has earned lots of attentions, especially in the field of remote sensing imaging. However, ghost imaging is a staring imaging technique, the imaging process for a certain scene usually needs plenty of samples, long exposure will result in the motion-deblurring and make a disadvantageous influence on the imaging quality. Thus, the imaging quality of ghost imaging in the situation of motion is a critical problem, and only by solving this problem perfectly, the practical application of ghost imaging may be meaningful. In this thesis, laser three dimensional ghost imaging in motion scenes is studied for the first time and we design and make a vehicle-borne testing system. The thesis is arranged as follows: In chapter 1, the background and research status of ghost imaging is introduced from the perspective of 3D imaging Ladar (Laser Detection and Ranging), and then make a conclusion of the merits and problems when ghost imaging technique is applied in the field of remote imaging. In chapter 2, firstly, the basic principle and implementation methods of static ghost imaging are introduced. Then, we make an investigation of the critical techniques for ghost imaging in the situation of moving scenes by theoretical and experimental study. Motion imaging methods based on different field of view, high pulse repetition frequency, multiple-input detection and photon counting ghost imaging are all introduced in this chapter. In chapter 3, a vehicle-borne testing system is introduced. The overall structure, static module and tracking module is introduced respectively from the aspects of optics, mechanics and electronics. In chapter 4, we take a brief discussion and summary of this thesis and made a plane for further study of ghost imaging
Theoretical and simulated investigation of optical system based on large diameter off-axis parabolic lenses
No full text大口径衍射光栅在惯性约束核聚变中有重要的应用，特别是高功率啁啾脉冲放大系统中的脉冲压缩光栅。但是通过全息曝光制造大口径、高质量衍射波面的光栅受到了曝光透镜的口径限制。近年来，离轴抛物面反射镜的应用越来越广泛，且制造技术已经越来越成熟。本论文主要对基于大口径离轴抛物面反射镜的光学系统进行了理论分析以及对脉冲压缩光栅波像差进行分析模拟，主要包含以下几个方面： （1）详细介绍了基于大口径离轴抛物面反射镜，通过单次曝光来制备全息光栅的光学系统，同时介绍了条纹锁定系统，并通过计算得出了小参考光栅的空间周期；并且分析了离轴抛物面反射镜以及激光器的参数要求。 （2）对离轴抛物面反射镜、轴对称抛物面反射镜、球面反射镜的成像特性进行了理论分析，并且模拟了以它们作为准直镜时制作的全息光栅的衍射波像差的变化。 （3）由于空间滤波器的三维位置要求非常的苛刻，非常微小的移动会使得全息光栅的衍射波像差产生很大的变化。故利用光学设计软件ZEMAX对该光学系统进行模拟，得到空间滤波器的位置变化对全息光栅衍射波像差的影响。并且当光学系统的波像差的PV值等于1/4波长时，光学系统的分辨率达到衍射极限，可以计算出空间滤波器的调节精度。 （4）对该光学系统的温度特性进行了详细的分析，主要包括通过光学设计软件ZEMAX模拟温度对脉冲压缩光栅的波像差影响，同时分析了温度对光栅的空间周期影响。并且对离轴抛物面反射镜表面镀有的金属膜或者多层介质膜对该系统偏振特性的影响。 （5）对现阶段正在进行的验证系统进行了分析，主要包括反射式曝光系统和透射式曝光系统。分别对这两种系统分析了温度对光栅波像差和光栅刻线空间周期的影响。Large-size diffraction gratings play important roles in inertial confinement fusion, particularly the pulse compressors in contemporary high-power chirped-pulse amplification laser systems. But to fabricate large-area gratings of high-quality diffraction wavefronts, the traditional method of holographic exposure requires large-aperture collimating lenses. In recent years, the off-axis parabolic lenses is more and more used in large diameter optical systems, and the manufacturing technology has been more and more mature. In this article, the optical system with large diameter off-axis parabolic lenses were adopted to achieve diffraction gratings by laser exposure. We analyzed the influences of optical properties, mainly includes the following several aspects: We introduced the optical system in detail which is based on the large diameter off-axis parabolic lenses to achieve diffraction gratings by laser exposure. We analyzed the fringe locking system and got the spatial period of the small reference grating by calculating. Meanwhile we calculated the parameters of the off-axis parabolic lenses and laser. We analyzed the imaging characteristic of off-axis parabolic mirror, axisymmetric parabolic mirror and spherical mirror in theory, and simulated the variations of the diffraction wavefronts of holographic grating fabricated by the optical system who took them as collimating lenses. Because the requirements of the position of space filter is very high, so we simulated the changes of the diffraction wavefronts aberration (called by PV value) caused by space filter changes by ZEMAX. When the PV value of the optical system is 0.25λ, the optical system would reach the diffraction limit. So the precision of the adjustment of spatial filter can be calculated. We analyzed the temperature characteristics of the optical system which includes simulating the changes of wavefronts aberration of pulse compression gratings caused by the temperature using ZEMAX, and calculating the influence of temperature on the spatial period of the grating. And the metal film or dielectric multilayer film that coating on off-axis parabolic lenses has a important impact on this system. For ongoing validation system - reflective exposure system and transmission exposure system, we carried on the analysis of the temperature characteristic which includes the changes of wavefronts aberration and spatial period of gratings caused by the temperature and wavefronts aberration caused by space filter changes using ZEMAX
Influence of Heat Accumulation on Surface Figure Controlling during Continuous Polishing
No full text本文围绕大口径超精密光学元件在环形抛光加工过程中遇到的难题，开展了 环形抛光中热积聚效应影响的研究，并实现了热积聚效应的有效抑制。 环形抛光技术以其良好的全频谱均匀去除能力、 收敛速度快、 加工精度高和 生产成本低等特点， 成为大口径光学元件加工的首选方式。 但是环形抛光技术目 前依旧存在着诸多不足， 如加工周期加工质量的可控性程度不高， 对操作者的经 验依赖性强等，其根本原因是人们对环形抛光的规律认识不够，尤其是一些工艺 参数的影响。 在这些影响因素中， 热积聚效应是极为重要的一个， 热积聚效应体 现在系统的温度分布及变化情况。 大口径光学元件、抛光胶盘等对热积聚效应非 常敏感。加工过程中温差引起的工件形变通常远远超过所要求的工件面形； 环境 温湿度的变化影响着热积聚效应导致抛光胶盘温度变化从而产生不同程度的蠕 变变形， 间接影响工件面形；检测时需长时间恒温，影响加工效率；不同材质的 工件在相同的工艺条件下因热积聚效应的不同， 所得面形不同，给加工带来很大 不便。 因此，本论文围绕着环抛过程中的热积聚效应，开展了相应的工作，主要 如下： 介绍了环抛过程中的热积聚效应，包括热积聚效应的形成及实验探测。 分析 了环抛过程中导致热积聚效应形成所涉及的热学现象，讨论了抛光过程中热量的 产生原因与散失机制及相关影响因素，为抑制热积聚效应提供了理论指导。对 ? 260 mm × 26 mm Nd:glass 工件温度分布情况进行了测量，获得了工件的加工 面径向温差及上下表面温差，证实了热积聚效应的存在。 研究了热积聚效应对环抛中面形控制的影响。 首先，对热积聚效应的影响进 行理论分析。使用有限元分析软件 ANSYS 对 ? 260 mm × 26 mm 同等大小不同 材质的工件在同等上下表面温差和径向温差下的形变进行了仿真。结果表明， 钕 玻璃热形变比 K9 和 ULE 要大，即使温差只有 0.1℃，所引起的热形变已远远超 过加工精度要求。然后，将三块 ? 260 mm × 26 mm 同等大小不同材质的工件置 于同一工件环中，在相同的加工条件下进行抛光对比实验， 探究不同材质工件受 热积聚效应影响的差异以及同一工件受热积聚效应影响的变化情况。结果发现： 钕玻璃受热积聚效应影响最大， 抛光过程中面形波动最为激烈；加工过程中，工 件受的热积聚效应并不是一成不变的，而是随着各影响因素的变化而出现一定程 度的波动。 研究了抑制热积聚效应的方法。运用循环注液并配合加深加宽沟槽的方法， 工件的上下表面温差及加工面径向温差得到一定程度的降低；并且加工过程中工 件面形线性收敛，面形也更加规则。 运用抛光胶盘改性的方法，在胶盘中掺杂石 墨，胶盘的热导率提高，及时导走了环抛过程中产生的热量， 并且降低了工件与 胶盘间的摩擦系数，减少了产热量，对抑制热积聚效应起到一定程度的作用。This thesis focuses on problem s encountered in continuous polishing of large aperture ultra- precision optical elements, carried out research in the influence of heat accumulation , and effectively inhibit ted heat accumulation effect. Having the advantages in full- spatial - frequency homogeneous removement, a high speed of convergence, a high precision of process and low production costs make continuous polishing the first choice for large aperture optical elements manufactur ing. However, there are still many problems in continuous polishing , such as low controllability of processing cycle and processing quality, strong dependen ce of the operator's experience. The primary cause is people's lacking understanding of the law to continuous polishing, especially the effect of some processing parameters. In all these processing parameters, heat accumulation effect is a significant one. Heat accumulation effect is reflected in the system of temperature distribution and changes. The large aperture optical elements and pads are very sensitive to h eat a ccumulation effect. The thermal deformation caused by temperature difference is far surpass processing precision required ; pads have different degrees of creep deformation on account of v ariety of environment temperature and humidity which affect heat accumulatio n , indirect ly effects the workpiece surface figure; it takes a long time to achieve constant temperature which affects the processing efficiency; different material of workpieces gain different surface figures in the same process conditions, owing to different extent h eat a ccumulation effect, which brings great inconvenience in processing. Therefore, this thesis carr ied out the corresponding work about the heat accumulation effect in continuous polishing , mainly as follows: Introduced the heat accumulation effect in continuous polishing process, including the formation and experimental detection. Analyzed the thermal phenomena involved in the continuous polishing process, discussed generation and dissipation of the heat during polishing process and the effect factors on these thermal phenomena, , which give rise to heat accumulation effect, provided a theoretical guidance to the inhibition of heat accumulation effect. Measured the temperature difference of ? 260 mm × 26 mm Nd:glass, obtained the temperature difference along the polishing surface and temperature difference between top and bottom surface, proved the heat accumulation effect to be existing. The results showed that workpieces of different aperture own different temperature difference, the larger the aperture, the bigger the temperature difference. Studied the influence of heat accumulation on surface figure controlling. First, s imulations were made about the deformation of ? 260 mm × 26 mm different material workpieces under variational temperature difference. The result shows that, with same temperature difference, Nd:glass deforms more severely than K9 and ULE . Even though the temperature difference is as tiny as 0.1°C, the deformations are far surpass processing precision required. Then, to explore the diverse influence of heat accumulation on workpieces of different material and the fluctuation of heat accumulation , three ? 260 mm × 26 mm workpieces were polished in one ring at the same time. It was found that: Nd:glass suffers the most from heat accumulation , owns the most intense surface figure fluctuation . And, the heat accumulation effect are not constant, it changes with the influencing factors. Researched on methods to restrain heat accumulation. By c irculation slurry injection with deepen an d widen the groove, both the temperature difference between the upper and lower surface of the workpiece and the temperature difference along the radial direction of the polishing interface are reduced to some extent; the surface figures are linearly convergent and more inerratic. By the method of doping graphite in pads, the thermal conductivity of pads increased, conducted the heat timely, to a certain degree of inhibition of heat accumulation effect
Endurance study on metal multilayer dielectric during chemical cleaning
No full text脉冲压缩光栅(Pulse Compressing Grating, PCG)是高功率激光系统中的重要元件，金属介质膜光栅(Metal Multilayer Dielectric Grating, MMDG)由于具有宽反射带宽、膜层数少、膜层内部应力小的特点，是脉冲压缩光栅的重要发展方向，为解决金属介质光栅膜在化学清洗时的分层及剥落问题，本文采用退火的方法，详细地探究了退火处理对金属双层膜与金属介质多层膜在应力、微结构与抗清洗性能方面的影响。 具体包括如下两个方面的工作： 1）研究了300℃下不同退火时间对金/铬双层膜的结构、形貌与应力的影响。实验结果表明：在退火过程中，铬原子将会与金以固溶体的形式从金膜下面的铬层中扩散到金膜的表面，与此同时，扩散到表面的铬原子将会被氧化，金膜表面累积的铬氧化物又会顺着金膜晶界向下扩散。本文详细讨论了在退火过程中铬原子的扩散过程与铬氧化物的逆向扩散过程对金膜应力的影响。 2）为了增强金属介质光栅膜的抗化学清洗能力，将电子束蒸发方法制备的金属介质光栅膜样品进行了不同温度的退火处理。实验结果表明高于300℃退火温度的工艺处理，样品具有很强的抗化学清洗能力，并在Au层与SiO2层的界面处观察到了过渡层的出现，从而探究了过渡层中的元素分布。机理研究表明：过渡层的形成主要是由于Cr原子从Au层的底部扩散到Au层的顶部和SiO2层的下界面形成的。该过渡层的存在增强了Au层与SiO2层的粘附力并且阻止了过氧化氢诱导的初始分层缺陷的形成，从而增强了抗化学清洗的能力。Pulse compression gratings (PCG) is an important element in high power laser systems. Metal multilayer dielectric grating (MMDG) is one of the important development direction of PCG because of the wide reflection bandwidth, less number of membrances and less internal stress of membranes. In order to solve the chemical delamination problem during chemical cleaning, this article detailedly explored the effect of annealing treatment on the stress, microstructure and endurance of chemical cleaning of MMDG. Followings are the main contents of the thesis: 1) Au films with thickness of 200 nm on 10 nm Cr as adhesive layers were fabricated on the fused silica by the electron beam evaporation method. The influence of post-annealing treatment on the microstructure, surface morphology and residual stress of the Au-Cr bilayer films were studied. It was found that Cr can diffuse to the surface of the films by formatting solid solution with gold during post-annealing and Cr was oxidized on the surface and diffuses downward along the grain boundaries in gold film. The diffusion mechanisms and origin of the residual stress were analyzed and discussed. 2) The influence of annealing treatment on the interface diffusion and chemical cleaning of metals/multilayer dielectric coating was studied. The multilayer fabricated by electron beam evaporation method is composed of Cr/Au/SiO2/HfO2/SiO2/HfO2/SiO2HfO2. A thin transition layer between Au and SiO2 was observed after annealing treatment. It is shown that Cr atoms diffuse from the bottom of Au layer to the top to form a transition layer, with the higher the annealing temperature the thicker the transition layer. The transition layer enhances the adhesion between Au film and SiO2 layer and blocks the formation of the peroxide-induced delamination defects, and it was found that annealing at temperature higher than 300℃the multilayer coating demonstrates a strong resistance chemical cleaning. The diffusing channel and driving force of Cr diffusion were analyzed and discussed
Study on Three-dimensional Array Focusing Properties of generalized Fibonacci Photon Sieves
No full text衍射光学元件在物理学和生命科学领域具有重要的应用前景。体积小、重量轻、设计灵活的光子筛作为一种新型的聚焦成像衍射光学元件受到越来越多研究人员的关注。另一方面，数学上的斐波那契数列被广泛应用在光学元件设计中，比如，多层线性光栅、环形光栅、涡旋波带片、双焦衍射透镜等。广义斐波那契数列的特性也是数学领域研究热点之一。本论文把广义斐波那契数列引入到光子筛等微纳结构设计中，提出了广义斐波那契光子筛结构的设计方法，研究了该器件的三维阵列焦点(m×n)×p特性，其中p代表焦平面个数，m×n代表某个焦平面上阵列焦点的数目，同时对提出的物理模型进行了模拟仿真和实验验证。具体研究内容主要概括为以下六点： 1、调研了广义斐波那契光子筛研究的背景和意义。重点调研对象是具有(1×1)×1特殊阵列焦点的传统光子筛、具有(1×1)×p特殊阵列焦点的多焦点光学器件以及具有(m×n)×p阵列焦点的光学器件。 2、介绍了光子筛衍射理论。重点介绍了筛孔标量衍射和矢量衍射理论，并以振幅型光子筛为例，分析了传统光子筛的聚焦特性。 3、提出了双焦斐波那契光子筛的一般性设计方法。提出通过筛孔位置和孔径大小控制轴上焦点光强分布的方案，同时引入超高斯调制技术对筛孔数目进行调制，进一步提高了广义斐波那契光子筛焦斑的横向分辨率。 4、探讨广义斐波那契光子筛轴上焦点分布内在的数学关系。其焦比(焦距之比)特性完全由广义斐波那契序列的数学特征决定，表现出一定的光学结构拓扑不变性。此外，还发现衍射光学杠杆效应。 5、在振幅型广义斐波那契光子筛的基础上发展出了相位型广义斐波那契光子筛，详细探讨了如何利用相位设计来获得双涡旋焦斑。 6、提出了利用广义斐波那契光子筛实现阵列焦点的方法。利用衍射光学杠杆效应和不同斐波那契序列设计出了混合式广义斐波那契结构，实现了混合阵列焦点功能。 广义斐波那契光子筛独特的聚焦特性，使其在光学开关、纳米光刻、生物仿生眼、多焦成像和测距，甚至在X射线显微技术和太赫兹成像技术都将有新的应用。Diffractive optical elements (DOEs) have a large number of new significant applications in physical and life sciences. Photon sieve (PS), in consequence of its small size, light weight and flexible design, is a new type of focusing and imaging DOEs, and given more and more attention of scientific researcher. On the other hand, Fibonacci sequence in mathematics has been employed in the development of different photonic devices, for example, multi-layers and linear grating, circular grating, spiral zone plates, and bifocal diffractive lenses. Meanwhile, the mathematical characteristic of generalized Fibonacci sequences is also a hotspot in the field of mathematics. Here, the generalized Fibonacci sequences are firstly introduced into the design of micro-nano structures, such as PS and Fresnel zone plate (FZP). Then, based on the above Fibonacci PS, three dimensional array (m×n)×p focusing properties are mainly discussed, where p is the number of focal planes and m×n represents array foci at focal planes. The simulation and experiments agree well with our proposed physical modeling. The research contents can be summarized as follows: 1. The research background of generalized Fibonacci photon sieves (GFiPS) is investigated in detail. The key researches include traditional photon sieve with (1×1)×1 array foci, axial multi-focal optical devices with (1×1)×p array foci and optical devices with (m×n)×p array foci. 2. The diffraction theory of PS is reviewed. The scalar diffraction and vector diffraction theory are mainly discussed. Taking the amplitude-only PS as an example, the focusing characteristics are analyzed in detail. 3. The design method of a bifocal GFiPS is proposed. The axial intensity distributions are controllable by adjusting the position and size of pinholes. Then Gaussian apodized technology is applied to GFiPS in order to further improve the resolution of the focal spots. 4. The mathematical relationship among the axial multiple foci generated by GFiPS is discussed. We find that the ratio of focal lengths is completely determined by the mathematical characteristics of the corresponding generalized Fibonacci sequences, which is called optical topological invariance. Besides, diffraction optical lever (DOL) is found. 5. The design method of phase-only GFiPSs is proposed. We study their focusing properties in detail, and then successfully get twin axial vortices. 6. Two technologies are presented to extend the number of layers in order to realize three-dimensional array foci. One is the diffractive optical lever; the other is multi-hybrid Fibonacci structures. The focusing properties of GFiPSs make them available for optical switches, nanometer lithography, bionic eyes, multi-focus imaging and ranging, even some new applications in X-ray microscopy and THz imaging