飞秒激光双光子微细并行加工方法

飞秒激光三维微细加工技术具有真三维的制作能力和亚微米的加工分辨率等特点，因此获得越来越多的关注，但其串行工艺加工效率低是其技术难点．为了提高加工效率，搭建了一套飞秒激光并行加工平台，利用微透镜阵列实现飞秒激光分束聚焦，初步实现了双光子微细并行加工，在光敏树脂和玻璃上分别并行加工出多个二维结构，加工单点分辨率达到1．25μm．针对实验结果，对实验的加工一致性和分辨率进行分析，提出了进一步提高加工效率和加工一致性的方法．     

飞秒激光三维微细加工技术

双光子吸收几率与光强度的平方成正比,因此,双光子吸收引发光致聚合局限在紧密聚焦的焦点区域,通过控制焦点的扫描运动可实现高精度三维加工。基于该原理,提出了一种利用飞秒激光进行微细加工的技术。根据此技术,建立了飞秒激光三维微细加工系统,该系统包括光源系统、显微镜系统、实时监测系统和精密移动系统等。研究发现,该系统加工的直线线宽最小可达500nm;加工线宽与加工速度成反比;激光功率为2mW时,最大和最小临界加工速度分别为80μm/s和1μm/s;制备出线宽1μm,宽度5μm的“CHINA”复杂结构,以及杆间距、层间距均为5μm的三维木堆型光子晶体结构。实验证实,该技术是一种非常灵活的微细加工技术。     

秒激光双光子微纳加工技术及其在光子学微器件制备中的应用

飞秒激光可以与包括玻璃、陶瓷、半导体、金属、塑料、树脂等各类物质产生相互作用,其相互作用原理不同,加工方法也不同。利用非线性光学效应——双光子吸收的飞秒微纳加工技术是最独特也是最具有应用前景的微纳加工技术。利用显微物镜将飞秒激光聚焦到加工介质时激光光强在焦点处呈三维空间分布,双光子吸收过程仅产生在具有足够激光强度的微小区域,通过控制激光光强可以调节双光子吸收的产生范围,在适当的激光强度时,可以突破光学衍射极限的限制,将双光子吸收过程控制到远小于激光波长甚至纳米尺度范围,从而达到进行纳米加工的目的。飞秒激光双光子微纳加工技术具有真三维、一次成型及高加工分辨率的特点,是三维微纳结构制备的理想工具之一。通过“理论计算-计算机辅助图形设计-微纳激光制造“这样一个简单的流程可以实现制备可设计的复杂三维微细结构,因此在光子学微器件、微机电系统等领域具有巨大的应用前景。最近几年双光子微细加工技术也已成功地应用到功能性光子学器件中。在制备基于光子晶体带隙原理的三维光子元器件及其立体集成方面,飞秒激光双光子方法具有无可比拟的优势。我们研究小组利用碳硅烷树状大分子修饰的激光染料与光聚合制备的光固化树脂,采用双光子聚合微加工技术制...     

双光子微加工技术与应用研究

双光子微加工技术是利用材料对飞秒激光束在焦点局部区域发生的双光子吸收现象，并通过逐点扫描来实现微器件三维成型的加工技术．介绍了双光子微加工技术的原理、特点和过程，描述了该加工技术的实验系统，并给出了部分利用该系统获得的初步实验结果，最后简单介绍了双光子微加工技术的一些实际应用。     

三维微细电火花伺服扫描加工工艺

为提高三维微细电火花加工的加工效率,从而达到工业应用目的,采用放电间隙伺服控制实时补偿电极损耗的技术路线,提出了三维微细电火花伺服扫描加工方法．基础实验验证了伺服扫描加工每层加工深度的一致性,研究了横向扫描加工速度对加工深度的影响规律．在小于1mm2加工区域内的三维结构加工实验结果显示,伺服扫描加工可以便捷地实现三维微小结构的加工成型．进一步在工件与电极之间附加激振,可大幅度地提高放电脉冲的有效利用率以及加工效率．采用φ100μm的钨丝电极,在铜试件上加工深度300μm的典型三维形状,加工时间小于50min．     

飞秒激光双光子聚合三维微纳结构加工技术

飞秒激光双光子聚合微纳加工技术作为重要的三维微纳结构制备手段，已成为国际前沿研究热点。该技术利用激光与物质相互作用的双光子非线性吸收效应和阈值效应，可以突破经典光学理论衍射极限，实现纳米尺度的激光加工分辨力，在三维功能性微纳器件制备领域正在发挥着十分重要的作用。本文在介绍飞秒激光双光子聚合三维微纳加工技术的光物理和光化学过程基本原理的基础上，重点回顾人们在改善加工线宽及分辨力、提高加工效率等方面的研究进展与发展概况。该技术所制备的各种微光学器件、集成光学器件、微机电系统以及生物医学器件，不仅充分展示了飞秒激光双光子聚合三维微纳加工技术的高空间分辨力和真三维加工特点，也为其在相关前沿领域的应用提供具有启发性的思路。最后，对该技术实现高精度、高效率、低成本、大面积、多功能的三维微纳结构加工所存在的挑战和未来发展方向，进行了讨论和展望。     

二维和三维微/纳高效精密加工中的纳立体刻印工艺

双光子聚合（TPP）是通过光敏剂中的非线性双光子吸收过程所引发的，其作为一种新工艺，自问世以来，已在二维和三维加工聚合应用领域中得到广泛研究．对于二维纳米图案的加工，纳复制工艺已经演变为体素模板扫描方法．该方法用黑白双色2块图作为设计图案，并转排成体素模板以控制聚焦激光素的开关．复杂的三维微结构也可以采用多重断面分层叠加的方法进行加工，各断面的扫描数据从三维CAD数据中得到．在聚合反应后，没有固化的液态树脂，其采用在树脂上浇注类似于酒精之类溶剂的方法去除，从而显露出聚合的微结构．在前期的工作中，已经成功地加工出了高空间分辨力的三维微光学器件，分辨力约为100nm．微机械器件和光子晶体等的近期研究工作提高了其TPP的效率和精度．介绍了近来开发的基于TPP的一些微加工工艺．     

在微细电火花铣削中介质对电极损耗的影响

在微细电火花加工（EDM）中电极损耗是不可避免的,而针对电极损耗的研究大都是在油工作液中,很少针对气中放电时的电极损耗进行研究．气中电火花加工普遍采用管状电极,所以为了获得尺寸更小的工件,通过反拷块可磨削出微米级的实心电极,并采用外部充气的方式,可实现微米级三维结构的气中电火花加工．实验考虑了影响气中放电电极损耗的各种因素．通过观察微细电火花三维铣削放电现象与结果,可得到气中放电的规律．由于电火花加工中电极损耗是不可避免的,所以在三维铣削加工中对电极进行在线检测并补偿,工件成形精度大大提高．对刀具路径进行合理规划,可以缩短加工时间．与油中电火花铣削相比,气中电火花加工时电极损耗更低,加工表面质量更好．     

一种微型转子的激光加工和光致旋转

利用单束强聚焦激光产生的光学力可以驱动微型器件,具有无机械接触和无需导线等优点,为微型机电系统提供了一种新型的驱动方式。在自行研制的飞秒激光微细加工系统中,采用一种新型的丙烯酸酯紫外光固化树脂,通过双光子聚合加工出直径6μm的万字形微转子。利用光镊装置实现了微转子的俘获,并在激光功率50mW时实现了转速为200rpm的光致旋转。微型转子的光致旋转为实现微机械马达提供了一种有效手段。     

微细电化学加工技术

开展了微细电化学加工技术的试验研究工作，内容包括微细电铸和微细电解加工．讨论了微细电化学加工的工艺特点和主要技术步骤．针对若干典型微结构，提出了相应的微细电化学加工方法和技术方案，采取了纳秒脉宽脉冲电流、电化学微铣削等手段，结合若干实例进行了加工试验，例如：微缝电解加工、微轴电解加工、微针尖电解加工及微齿轮模具模芯电铸成型等，获得了很好的试验结果．提出的加工方法在金属零件微制造方面有着重要的应用前景．     

Second‐Harmonic Generation from a Single Core/Shell Quantum Dot

Nanoparticles emitting two‐photon luminescence are broadly used as photostable emitters for nonlinear microscopy. Second‐harmonic generation (SHG) as another two‐photon mechanism offers complementary optical properties but the reported sizes of nanoparticles are still large, of a few tens of nanometers. Herein, coherent SHG from single core/shell CdTe/CdS nanocrystals with a diameter of 10 to 15 nm is reported. The nanocrystal excitation spectrum reveals resonances in the nonlinear efficiency with an overall maximum at about 970 nm. Polarization analysis of the second‐harmonic emission confirms the expected zinc blende symmetry, and allows extraction of the three‐dimensional nanocrystal orientation. The small size of these nonlinearly active quantum dots, together with the intrinsic coherence and orientation sensitivity of the SHG process, are well adapted for ultrafast probing of optical near‐fields with high resolution as well as for orientation tracking for bioimaging applications.     

立体微型器件的微制造技术及其在微机电系统(MEMS)的应用

综述了近年来与微型机电系统（MEMS）相关的材料微制造和微加工技术的最新研究进展.重点介绍了如何利用硅晶片作为微型模具来制备压电陶瓷和热电材料的微型柱状阵列结构和反应烧结碳化硅微型转子等微制造技术,并展望了材料微制造技术在研制微型医疗器件和微型移动能源方面的应用前景.     

Liquid sheet instability

Summary A linear instability analysis is presented for an inviscid liquid sheed emanated into an inviscid gas medium. The influence of Weber number and gas to liquid density ratio on the evolution of two and three dimensional disturbances of symmetrical and antisymmetrical type is studied. It is found that two dimensional disturbances always dominate the instability process at low Weber number. When the Weber number is large, symmetrical three dimensional disturbances become more unstable than two dimensional ones for long waves. The effect of increasing the gas to liquid density ratio is to promote the dominance of long three dimensional symmetrical waves over their two dimensional counterpart. For antisymmetrical waves, two dimensional disturbances always prevail over three dimensional disturbances regardless of Weber number or gas to liquid density ratio especially for long waves. For short waves, both two and three dimensional disturbances grow at approximately the same rate. It is demonstrated that a critical Weber number exists, above which three dimensional disturbances become unstable. Furthermore, a finite wave number is necessary for the onset of three dimensional instability. The wave number range that leads to a higher growth of, symmetrical three dimensional disturbances than two dimensional ones is investigated. An explanation of the differences in the behavior of three dimensional symmetrical and antisymmetrical instabilities is provided.     

Inside Front Cover: Experimental Evidence for Superprism Effects in Three‐Dimensional Polymer Photonic Crystals (Adv. Mater. 2/2006)

The inside cover illustrates the highly dispersive propagation of light in a three‐dimensional polymer photonic crystal. White light is coupled into a woodpile structure and split into its wavelength components due to the frequency‐dependent dispersion properties of the structure. This superprism effect is orders of magnitudes higher than in a conventional glass prism and is caused by the strong anisotropy of the dispersion surface at frequencies slightly above the photonic bandgap. In work reported on p. 221, Serbin and Gu fabricated these woodpile structures operating in the near‐infrared wavelength range by means of two‐photon polymerization and give theoretical and experimental evidence for the superprism effect in these low‐index photonic‐crystal structures.     

3D EBSD characterization of deformation structures in commercial purity aluminum

A method to map the microstructure in deformed aluminum in three dimensions is presented. The method employs serial sectioning by mechanical polishing, and electropolishing to obtain a good surface quality, and orientation mapping of individual grains in each section by electron backscattered diffraction. Techniques to carefully align the sample and to accurately measure the thickness of the material removed in each serial section are described. A new method for stacking the two dimensional maps together to produce a three dimensional visualization of the microstructure is presented. The data are analyzed in terms of the deformation-induced orientation spread within each grain. In particular the advantage of using three dimensional data, as opposed to two dimensional data, is illustrated, by inclusion of information about the three dimensional morphology of a grain and its neighbors.     

大口径多孔透镜离轴成像研究

设计并采用微细加工技术制作了直径D=50mm,特征尺寸为10μm的大口径多孔透镜(photon sieve).在一定的视场下采用数值计算和实验方法分析了其聚焦特性和MTF曲线,为克服多孔透镜一级衍射效率较低,成像质量受背景光干扰的影响,采用了同轴和离轴成像实验.实验结果与聚焦特性一致,两种实验方法得出的不同实验结果表明:离轴成像系统效果克服了同轴成像受0级背景光的影响,改善了像质,为很多一级衍射效率较低的衍射透镜成像提供一种新的成像方式.     

三维动态位移测量装置

本文设计出一种用于测量运动物体在三维空间动态位移的测量装置，它主要用于测量自行火炮车辆在射击过程中的振动轨迹（平面和空间的）及三维运动位移－时间历程曲线，也可直接用于其它运动物体的测量，本文详细地描述了该装置的工作原理及结构，并进行了理论分析。     

基于块体形状分类的爆堆块度三维几何参数估算

爆堆图像分析法是统计爆破后矿岩块度分布的主要方法,针对图像分割后得到的岩块二维图形,研究了通过岩块二维投影几何参数估算岩块体积的方法。统计分析岩体中节理面倾向、倾角和间距的概率分布,通过Monte Carlo随机模拟三维节理面网络,建立节理面切割的矿岩原始块度三维模型,利用3组相互垂直的平面切割块度三维模型获取块体二维轮廓。对于不同的二维形状参数φ值区间,分析三维形状参数ε和κ的变化规律并建立其与φ的关系式。利用块体形状分类方法将块度三维模型分成6个块体集合,根据形状假设理论,由统计数据得出块体实际体积的对数和球形假设估算的块体体积的对数呈线性相关,应用回归分析推导出得到通过三维形状参数估算岩块体积的公式,通过实验对比,根据二维几何参数估算的块体体积和块度模型的块体实际体积的分布规律一致。     

Pinhole-array x-ray spectrometer for laser-fusion experiments

A pinhole-array x-ray spectrometer for laser-fusion experiments is demonstrated. An array of approximately 300 pinholes is placed in front of a flat-crystal spectrometer, yielding target images at photon energies ~10 eV apart (for photon energies of ~4 to 5 keV). For wideband radiation the images are two dimensional, whereas when a single spectral line is used, the field of view in the direction of dispersion is limited. However, single spectral line images can have a field of view sufficient for imaging the compressed target core. We show the image at the Ti-Kalpha-line fluorescence from a Ti-doped shell, which we show to be excited by continuum radiation from the compressed core. The Kalpha image delineates the cold, compressed shell at peak compression, which can otherwise be obtained only through backlighting. In addition, the array provides spectra of high spectral resolution because of the reduction in the effective source size.     

Stability Regions and Spectra of Discrete Third-Order Autoregressive Time Series

This paper presents an analysis of third order autoregressive time series. The parameter regions, in the three dimensional parameter space, that produce the six separate types of power spectral density are analyzed. The study reveals that when a particular two dimensional cross section of the three dimensional parameter space is taken, the region of stability is always triangular. Within each triangular stability region in this two dimensional space, subregions which produce the six possible types of spectral shape are indicated. From these subregions it is possible to approximately choose the parameters necessary to model a process whose power spectral density contains at most two critical frequencies (maxima and minima).