薄膜G-T腔结构的空间波分解复用器设计

结合全通滤波器的设计方法,利用一维薄膜光子晶体的超棱镜效应,设计了一种G-T腔(Gires-Tournois腔)型薄膜空间波分解复用器,可在特定波段得到线性大空间色散,实现对入射光束的空间解复用作用。文中针对850nm波段进行了具体设计,以低折射率材料为腔材料,采用Sub H(LH)M1[(LL)C1]H(LH)M2[(LL)C2]H(LH)M3[(LL)C3]…的膜系结构,在844~856nm的范围内得到约19.3μm的线性空间色散位移。     

Optical fringe effects at prism borders in human tooth enamel sections

When ground sections of mammalian teeth are viewed under the light microscope each enamel prism appears to be surrounded by a prism sheath about 0.5 μm] wide. Seen by the electron microscope these sheaths are at most 0.1 μm wide. Because this dimension is beyond the resolving power of the light microscope it is difficult to explain the origin of the optical image. Optical fringes are frequently seen at the borders of transversely cut enamel prisms. The widths of these fringes have been measured under different optical conditions. It is concluded that the fringes are produced due to interference between direct light rays and those reflected from prism borders. A requisite for clear fringe production is that the reflectance of the prism border should be high. This high reflectance could only be achieved if prisms are separated from each other by material having a refractive index which differs significantly from that of the prisms themselves. It is therefore suggested that prisms are separated by a protein layer. It is then possible to explain why prism sheaths appear 0.5 μm wide under the light microscope. Study of mammalian tooth enamel by light microscopy suggests to the observer that the 5 μm wide rods (generally referred to as prisms) which constitute the enamel are each partially surrounded by a ‘sheath’ about 0.5 μm wide. Micro-radiographs indicate that the sheath is considerably less mineralized than the body of the prism (Glas, 1965). In contrast, from direct observation of enamel sections by electron microscopy, it has been concluded that no prism sheath exists and that prisms are separated by an interface which is bordered on its two sides by differently orientated crystals (Helmcke 1960, 1967; Ronnholm, 1962; Meckel, Griebstein & Neal, 1965). Between these two extremes are some electron microscope observations appearing to demonstrate the presence of a 0.1 μm wide membrane-like prism sheath devoid of inorganic crystals (Frank & Nalbandian, 1967) or an irregular region of microporosity where the different orientation of adjacent crystals results in a packing defect (Johnson, 1967). Any enamel section observed with the electron microscope may well have been distorted during its preparation for examination. Shrinkage due to dehydration is one of the most likely artifacts. Because the amount of the distortion cannot be known with accuracy it is difficult to decide which of the above electron-microscope appearances is closest to the actual structure of the prism boundary during life. It has recently been observed that when viewed end-on, the borders of prisms frequently appear as light striations (Osborn, 1968 and in press). In the present investigation the widths of these light striations have been measured under different optical conditions on an enamel section which was maintained in a hydrated condition. It was thought that this data on the optical properties of the hydrated prism boundary could be used to predict the structure of the boundary in vivo. A similar shrinkage is to be expected in sections examined with the light microscope because these have usually been dehydrated prior to mounting. It is therefore reasonable to try to relate the 0.5 μm wide optical image seen with the light microscope to the two different structures observed with the electron microscope. If no prism sheath exists it might be argued that the refractive index variation between the borders of adjacent prisms could in some way account for the production of the optical image. However, because this variation is probably less than 0.02 (Fremlin & Mathieson 1964) it is not clear how it could be used to explain the high contrast of the optical image. Furthermore, even if a 0.1 μm wide prism sheath exists, it is significantly thinner than the wavelength of visible light; again it is not clear how its presence results in the production of an image in the light microscope.     

Measurement of the refractive index dispersion of As2Se3 bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range

The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 μm range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.     

改进的迈克尔逊干涉仪测量薄膜厚度

为了测量未知折射率或不透明薄膜的厚度,借助力传感器对传统迈克尔逊干涉仪加以改进,并运用等倾干涉的原理结合抵消法设计了测量装置。薄膜被等厚的空气层所代替,通过间接测量,避开了机械螺旋空程差造成的影响,使用力传感器有效减小了挤压形变引起的误差。该装置测量范围为0.3μm～1.5mm,分辨力为0.3μm。实测数据表明,该装置具有良好的重复性和准确性。     

光学薄膜中的偏振效应

介绍了薄膜偏振效应的基本理论.光学薄膜在光倾斜入射时可等效为一线偏振器和一位相延迟器,这一特性可以用琼斯算法进行描述.利用薄膜的这一特性可以消除光学系统中不想要的偏振效应以保持光的偏振状态,也可以用来制作薄膜位相延迟片.用琼斯算法对YAG激光用全反射角立方反射镜的偏振特性进行了分析,并利用薄膜的偏振特性设计了两膜系对其进行了补偿;最后对一全介质高反射膜的相移特性进行了分析和优化设计,得到了一偏振保持高反射膜.     

Wide-band acousto-optic deflectors for large field of view two-photon microscope

Acousto-optic deflector (AOD) is an attractive scanner for two-photon microscopy because it can provide fast and versatile laser scanning and does not involve any mechanical movements. However, due to the small scan range of available AOD, the field of view (FOV) of the AOD-based microscope is typically smaller than that of the conventional galvanometer-based microscope. Here, we developed a novel wide-band AOD to enlarge the scan angle. Considering the maximum acceptable acoustic attenuation in the acousto-optic crystal, relatively lower operating frequencies and moderate aperture were adopted. The custom AOD was able to provide 60 MHz 3-dB bandwidth and 80% peak diffraction efficiency at 840 nm wavelength. Based on a pair of such AOD, a large FOV two-photon microscope was built with a FOV up to 418.5 μm (40× objective). The spatiotemporal dispersion was compensated simultaneously with a single custom-made prism. By means of dynamic power modulation, the variation of laser intensity within the FOV was reduced below 5%. The lateral and axial resolution of the system were 0.58-2.12 μm and 2.17-3.07 μm, respectively. Pollen grain images acquired by this system were presented to demonstrate the imaging capability at different positions across the entire FOV.     

Development of an ultra precision machine tool for micromachining on large surfaces

The goal of this research is to develop a multi-functional ultra precision machine to generate micro features on large surfaces. Design and characteristic analyses of our machine are presented. The analyses include its structural analysis and accuracy tests. Each axis of the developed machine was corrected and/or compensated from accuracy tests enough to generate grooves on workpieces with a less than 10 μm pitch size. After compensation, the 2-dimension position error between X-axis and Y-axis was reduced to 1.4 μm for a 400×400 mm² surface. From a 24 hours relative thermal displacement test between Y-axis and Z-axis, the machine showed a stable thermal displacement which was measured to be less than 1 μm. From groove machining tests, our machine could successfully generate 5 μm and 10 μm pitch grooves and showed a stable micro machining characteristics. From this research, we can conclude that the developed machine has mechanical characteristics enough to generate less than 10 μm pitch grooves on a 400×400 mm² surface.     

Sub-structure characterization of experimentally and naturally deformed ice using cryo-EBSD

In this work, we present first results of high‐resolution EBSD for ice with a spatial resolution down to 0.25 μm. The study highlights the potential of EBSD to significantly increase our understanding of deformation and annealing processes associated with the build‐up of internal stresses due to strain incompatibility between grains. Two polycrystalline samples were analyzed: a natural sample of polar ice from the Vostok ice core (Antarctica) and an experimentally deformed sample of laboratory grown columnar ice. In summary, we observe the following: (1) inhomogeneous deformation through the grains is translated into lattice distortions that are concentrated mainly at grain boundaries and triple junctions (natural and experimental sample), (2) these distortions may be continuous (natural and experimental sample) or may form distinct tilt boundaries and sub‐grains of 10–50 μm size (experimental sample). These form mainly by rearrangement of basal edge dislocations into low‐energy configurations (i.e. tilt boundaries) in various prism planes. Continuous lattice distortions originate from screw or mixed edge and screw dislocations lying in the basal plane.     

摩擦副表面沟槽型织构润滑性能的数值仿真

从目前的研究来看,织构的深度和载荷对油膜的润滑性能具有显著的影响,然而,在载荷变化的情况下,润滑膜的最小膜厚和黏性阻力是一个动态变化的过程。因此不同载荷下,最佳织构深度的选取还需系统地进行分析。通过建立沟槽型织构流体润滑模型,分析了织构的深度以及承载力对摩擦副的油膜厚度、压力、剪切力、以及摩擦因数的影响。结果表明：在承载力一定时,油膜厚度随织构深度的增加呈先增大后减小的趋势。在89 N载荷下时,存在最佳油膜厚度6.4184μm,此时织构深度为2.97μm,摩擦因数为0.0162。     

中红外双通道滤波器的研制

针对中红外目标探测需求,采用多个截止带拼接的设计方法,结合TFCal膜系设计软件优化各个膜层厚度,得到了中红外双通道滤波器膜系。通过对膜系敏感层的分析,将总膜系分成两个膜系进行镀膜,成功制备出2.7~3.0μm和4.1~4.4μm双通道滤波器。得到的样品在2.7~3.0μm波段平均透过率为73%,在4.1~4.4μm波段平均透过率为81%。该方法提高了膜系设计效率,减少了膜层数和总厚度,可解决膜系过厚带来的开裂和脱膜等问题,节约了镀膜时间和成本。     

谱线弯曲对成像光谱仪辐射信号采集的影响

为了研究谱线弯曲对棱镜色散成像光谱仪光谱辐射信号采集的影响。首先,给出探测器像元采集到的辐射能量的表达式。然后,结合复合棱镜的色散特性,在可见近红外光谱范围（400～1000nm）内,计算当光谱偏离量为0.01d、0.1d和0.5d（d为探测器像元尺寸）时系统采集到的辐射能量与没有谱线弯曲情况下系统采集到的辐射能量的归一化差值,衡量谱线弯曲下系统辐射测量的变化。结果表明：谱线弯曲引起的探测器上的光谱偏离导致系统辐射信号采集发生变化,与没有谱线弯曲的情况相比,采集到的景物辐射信号在大气吸收带的边缘出现明显的偏差,且信号的差值随光谱偏离量的增大而增大,当光谱分辨率提高时,一些较弱的吸收峰附近也会出现明显的信号偏差。对于光谱分辨率平均为10nm的成像光谱仪,谱线弯曲量应控制在0.3nm以内。     

A method for the fabrication of thin-foil apertures for electron microscopy

A method is described for making thin foil apertures by piercing a plastic film with a heated microneedle and subsequently metallizing the plastic film by vacuum evaporation. Apertures can be made with diameters from 5 μm to 100 μm. They are round and very sharp-edged and can be made in various patterns and combinations of sizes.     

倾斜入射条件下衬底对金属网栅屏蔽特性的影响

提出了双层膜系分析方法,该方法采用独立网栅等效薄膜模型,将网栅对衬底干涉的影响引入分析,克服了Kohin方法仅考虑衬底干涉的不精确性,并避免了其分析独立网栅的透波率公式在高频和大入射角时存在的不准确性。用紫外光刻在石英衬底上制备了周期为320 μm,线宽为4.5 μm的网栅,测得S波30°入射时12~18 GHz的屏蔽效率大于16 dB,略低于理论值但变化趋势一致,证实了双层膜法的有效性。进而分析衬底影响表明:入射为S波及小于衬底布儒斯特角θ_B的P波时屏蔽效率降低,而入射为大于θ_B的P波时屏蔽效率反常增加;屏蔽效率变化最大值随入射角变化;优化衬底厚度可在不影响网栅透光能力的同时获得最佳屏蔽效果。     

硅微光机械加速度地震检波器中M-Z光波导干涉仪结构设计

提出了一种新型的硅基M-Z干涉型光电集成加速度地震检波器。对硅基微光电机械加速度地震检波器的M-Z光波导干涉仪系统进行了系统研究和优化设计,采用K9玻璃作为基底层和包层材料,Bak7玻璃作为波导层材料,波导的宽度为4 μm,厚度为0.4 μm。M-Z光波导干涉仪的Y分支设计中采用上升反正弦S型弯曲,为适用于该干涉仪的信号臂和参考臂大跨距的特殊结构,应用波导转向镜实现了大角度光路转折,反射转向镜的内介质采用镀制金属铝膜得以实现,并利用BPM进行了仿真。为了防止TE模偏振光的偏振态经铝膜全反射后发生变化,加了4个长度为1 mm的TE模偏振器以保持其偏振态。实验结果与理论相符。     

表面等离子体共振理论仿真研究

为了掌握影响激发表面等离子体共振(SPR)现象的因素,文中以薄膜光学理论为基础,利用Winspall软件模拟研究Kretschman结构下,金膜厚度、待测介质折射率以及三棱镜类型对表面等离子体共振吸收峰位变化的影响,得出了最佳膜厚以及影响激发SPR现象的棱镜折射率和待测物质折射率随共振角度变化的规律,为SPR传感器的设...     

纯金膜表面等离子增强的旋光效应

为了研究棱镜的磁光特性对系统光学响应的影响,测试了单个BK7棱镜在全内反射条件下的旋光角度谱以及BK7棱镜与金膜组合构成Kretschmann结构的旋光角度谱,并根据传统光学理论分析了光谱的成因.理论分析结果表明:在单个BK7棱镜构成的全内反射结构中,棱镜底部对p波和s波产生的反射系数差异是导致系统进入全内反射临界角之前产生较强旋光效应的主要原因;在BK7棱镜与金膜组合构成的Kretschmann结构中,棱镜的磁光特性使得光波到达金膜表面之前产生了较小的s光分量,金膜表面等离子共振激发削弱了p光振幅,两种因素结合产生了一种新的表面等离子共振增强磁光效应的物理机制.实验结果表明:Kretschmann模式下,26 nm厚金膜的表面旋光角最大为1.7°,克服了传统磁光克尔效应响应较弱的缺点.     

光学薄膜的堆积密度及密度均匀性的分析与计算

光学薄膜的堆积密度通常是利用薄膜在真空及大气中折射率的变化来计算,在ＩＡＤ实验中,我们发现有些薄膜的堆积密度大于１．０,这意味着薄膜的密度比自然界中的材料密度还要密积,原因是薄膜具有较大的内压应力,我们还发现了薄膜的波漂不依从于堆积密度。这是因为它们在不同的蒸发条件下具有不同的密度均匀性,在用ＥＢ及不同条件的ＩＡＤ的情况下,我们计算并分析了堆积密度及密度均匀系数,并用ＳＥＭ 观察了薄膜的微结构。     

Water film thickness measurement system for oil-water pipe flow

A new technique development for high spatial and temporal resolution film-thickness measurement in oil-water flow is presented in this work. A capacitance measurement system is proposed to measure thin water films or local water fractions near to the pipe wall. The measurement system is based in a planar sensor which is flexible and can be placed close to and following the curvature of the inner wall of the tube. Experimental results of the capacitive technique showed that the system is able to measure film thickness between 400 μm and 2200 μm. Dispersed and core-annular flows were studied in a vertical 12-m-height glass pipe with 50.8 mm of internal diameter, using mineral oil (860 kg/m3 of density and 220 mPa s of viscosity) and tap water. Local time-domain signals and axial and circumferential distributions of water film thickness near to the pipe wall and 3-D images of water film are presented. The measured film thickness, obtained by the proposed technique, was compared with that obtained through a camera-based imaging technique and the agreement was good, with a deviation less than 20%. The new technique allows the observation and characterization of average interfacial topologies in separated flows, and high frequency phenomena related to dispersed flows that occur in liquid-liquid flow near the pipe wall.     

润滑油膜厚度的光学相干层析成像测量

为了对滑动轴承的润滑油膜厚度进行精确测量,搭建了光纤结构的谱域光学相干层析成像(OCT)检测系统。该检测系统通过谱域OCT对油膜进行高分辨率成像,根据一维深度图像和二维层析图像中油膜和轴承表面的相对位置得到油膜厚度。分析了SD-OCT的检测原理,并对油膜厚度进行了测量,通过干涉光谱解耦法减小噪声对测量结果的影响。实验结果表明,该系统的测量误差小于2μm,具有良好的重复性和可靠性。该测量方法能够对油膜进行快速准确测量,有望应用于机械设备轴承运行状况的在线监测。     

表面织构的深度影响润滑油膜承载能力的机制研究

采用基于N-S方程的CFD方法,研究最小油膜厚度为4μm时圆弧凹槽表面微织构深度的变化对动压润滑效果的影响,并深入探讨其机制。结果表明,在一定的工况条件下,凹槽深度不同,其承载性能存在一定的差异,当凹槽深度小于4μm时,随织构深度的增加其承载能力逐渐增强,当凹槽深度大于4μm时,随织构深度的增加其承载能力逐渐减弱,即深度值在4μm左右时油膜的承载能力最强。分析发现,织构深度的变化改变了润滑油流场的流动,深度增大到某个值时润滑油开始出现逆流现象,随着凹槽深度的增加,逆流区变大;逆流的存在削弱了织构的承载能力;速度不影响润滑油的流动走向,但会影响承压能力的大小;织构截面形状对润滑油的流动走向有影响,但对织构底部形成漩涡的规模大小影响不大,对润滑油膜承压能力影响不大。