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Liquid crystal composites as a route to 3D nanoparticle assembly 液晶复合材料作为3D纳米颗粒组装的途径
Pub Date : 2017-06-16 DOI: 10.1117/2.1201702.006865
L. Hirst, Sheida T. Riahinasab, C. Melton
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引用次数: 4
Novel semiconductor membrane external-cavity surface-emitting laser 新型半导体膜外腔表面发射激光器
Pub Date : 2017-06-13 DOI: 10.1117/2.1201703.006864
H. Kahle, C. Mateo, U. Brauch, R. Bek, M. Jetter, T. Graf, P. Michler
Optically pumped semiconductor vertical external-cavity surfaceemitting lasers (VECSELs) exhibit many desirable properties1, 2 and have therefore become an important stand-alone class of solid-state lasers over the last 20 years. For example, VECSELs can be used nowadays to reach 100W-level continuous wave output.3 However, a large quantum defect (resulting from the energy difference between pump and laser photons) means that heat is incorporated into the active region of VECSELs. This gives rise to a strongly temperature-dependent performance4 caused by the interplay of gain and cavity resonance and the limited charge-carrier confinement. The limited charge-carrier confinement is a particular challenge in the aluminum gallium indium phosphide (AlGaInP) material system, i.e., in which the thermal conductivity5, 6 is low and the laser structure is based on a thick distributed Bragg reflector (DBR). Indeed, the thermal conductivity of this type of DBR is an order of magnitude lower than well-conducting metals (i.e., which are often used as backside heatsinks) and two orders of magnitude worse than diamond (commonly used for the backside or as an intracavity heat spreader).7 In addition, the semiconductor structure itself—with a thickness of several micrometers (for the active region and the DBR)—and the substrate (with a typical thickness of 350 m) impede the heat flow out of the active region. To overcome the heat flow problems and to improve the performance of VECSELs, numerous thermal management strategies have been previously proposed. Such approaches include changes to the heat spreader arrangement,8 removing the substrate,1 flip-chip processes,9 or the insertion of compound mirrors.10 According to the natural progression of these Figure 1. Picture of the semiconductor membrane external-cavity surface-emitting laser (MECSEL) in operation. From left to right, the out-coupling/resonator mirror, diamond-sandwiched semiconductor gain membrane (integrated into a brass mount), birefringent filter, and pump optics with a 532nm pump laser beam (behind the birefringent filter), and a highly reflective resonator can be seen (as illustrated schematically in Figure 2).
光泵浦半导体垂直外腔表面发射激光器(VECSELs)表现出许多理想的特性1,2,因此在过去的20年中已成为一个重要的独立类别的固态激光器。例如,现在使用VECSELs可以达到100w级别的连续波输出然而,一个大的量子缺陷(由泵浦光子和激光光子之间的能量差造成)意味着热量被吸收到VECSELs的活动区域。由于增益和腔共振的相互作用以及有限的载流子约束,这就产生了强烈的温度依赖性能。在磷化铝镓铟(AlGaInP)材料体系中,有限的载流子约束是一个特别的挑战,即热导率5,6较低,激光结构基于厚分布布拉格反射器(DBR)。事实上,这种类型的DBR的导热性比导电良好的金属(即,通常用作背面散热器)低一个数量级,比金刚石(通常用于背面或作为腔内散热器)差两个数量级此外,半导体结构本身——厚度为几微米(用于有源区和DBR)——和衬底(典型厚度为350米)阻碍了热流从有源区流出。为了克服热流问题并提高VECSELs的性能,以前已经提出了许多热管理策略。这些方法包括改变散热片的布置,8去除基板,1倒装芯片工艺,9或插入复合反射镜根据这些的自然进程图1。图为运行中的半导体膜外腔表面发射激光器(MECSEL)。从左到右,可以看到外耦合/谐振镜,金刚石夹层半导体增益膜(集成到黄铜支架中),双折射滤波器,带有532nm泵浦激光束(在双折射滤波器后面)的泵浦光学器件,以及高反射谐振器(如图2所示)。
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引用次数: 0
Monitoring short-lived climate pollutants by laser absorption spectroscopy 激光吸收光谱法监测短期气候污染物
Pub Date : 2017-06-12 DOI: 10.1117/2.1201704.006896
Weidong Chen, Gaoxuan Wang, Dong Chen, Fengjiao Shen, H. Yi, R. Maamary, P. Augustin, M. Fourmentin, E. Fertein, M. Sigrist
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引用次数: 0
Hydrogen production with holes: what we learn from operando studies 孔制氢:我们从歌剧研究中学到的东西
Pub Date : 2017-06-08 DOI: 10.1117/2.1201704.006793
A. Braun, R. Toth, Kelebogile Maabong, M. Diale
As we become more aware of the limited amount of energy available from traditional sources, we are increasingly turning to solar power as a viable alternative.1, 2 Of the total worldwide energy consumption, 20% is electrical, with an increasing share being produced by photovoltaics. Scientists, engineers, technologists, and investors are now working towards a renewable alternative for the remaining 80%, which is currently obtained from fossil fuels, nuclear fuels, and biomass.3–5 Photoelectrochemical cells (PECs), which use sunlight to convert water into solar-hydrogen fuel, represent one route to achieving a renewable energy source. PECs are based on semiconductor photoelectrodes,6 but their principles of energy conversion and storage are analogous to photosynthesis. The photoelectrodes within PECs are comprised of two electrodes. At least one contains a light absorber (which is applied as a coating on a transparent conducting oxide, TCO) and one has an electrocatalytic surface (e.g., an aqueous-electrolyte coating). When light strikes the absorber, photoelectrons and holes are created. The electrons then migrate through the TCO, which acts as a current collector, and enter the electric circuit. The holes diffuse to the electrode surface, where they chemically react with water molecules and cause them to electrochemically split into oxygen gas. This gas evolves at the photoanode and can be collected in a container for any potential further use. Protons migrate through the electrolyte to the counter electrode, where they combine with electrons to form hydrogen gas, which is collected as fuel. We have designed a PEC reactor (a prototype of which is shown in Figure 1) that has a large (10 10cm) iron oxide Figure 1. The photoelectrochemical cell (PEC) reactor prototype. The device has an active area of 100cm2 and is comprised of glass coated with an iron-oxide photoelectrode. The design incorporates an oxygen gas outlet (top left). The white compartment on the right of the device holds the platinum counter electrode for hydrogen gas evolution and collection. One molar mass of potassium hydroxide, acting as the electrolyte, is supplied continuously.
随着我们越来越意识到传统能源的有限性,我们越来越多地将太阳能作为一种可行的替代能源。1,2在全球总能源消耗中,电力占20%,而光伏发电所占的份额越来越大。目前,科学家、工程师、技术人员和投资者正致力于开发一种可再生能源,以替代目前从化石燃料、核燃料和生物质能中获得的剩余80%的能源。3-5个光电化学电池(PECs),利用阳光将水转化为太阳能氢燃料,代表了实现可再生能源的一条途径。PECs以半导体光电极为基础,但其能量转换和储存的原理与光合作用类似。PECs内的光电极由两个电极组成。至少一种包含光吸收剂(其作为涂层涂在透明导电氧化物TCO上),并且一种具有电催化表面(例如,水电解质涂层)。当光线照射到吸收剂上时,就会产生光电子和空穴。然后电子迁移通过TCO,作为一个电流收集器,并进入电路。这些孔扩散到电极表面,在那里它们与水分子发生化学反应,并使它们在电化学上分裂成氧气。这种气体在光阳极处形成,可以收集在容器中以备将来使用。质子通过电解质迁移到对电极,在那里它们与电子结合形成氢气,氢气被收集作为燃料。我们设计了一个PEC反应器(其原型如图1所示),该反应器具有大(10 10cm)氧化铁(图1)。光电化学电池(PEC)反应器原型。该装置的有效面积为100cm2,由涂有氧化铁光电极的玻璃组成。该设计包含一个氧气出口(左上)。该装置右侧的白色隔间容纳用于氢气演化和收集的铂对电极。一摩尔质量的氢氧化钾作为电解液连续供应。
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引用次数: 0
Multi-projection 3D displays using multiplexing techniques in autostereoscopic displays 在自动立体显示器中使用多路复用技术的多投影3D显示器
Pub Date : 2017-06-06 DOI: 10.1117/2.2201705.03
Byoungho Lee, Soon-gi Park, Keehoon Hong, Jisoo Hong
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引用次数: 0
A new signal-amplification mechanism discovered in semiconductors 在半导体中发现一种新的信号放大机制
Pub Date : 2017-06-05 DOI: 10.1117/2.1201701.006843
Y. Lo, Yu-hsin Liu, D. Hall, Ifikhar Ahmad Niaz, Mohammad Abu Raihan Miah
Preamplifiers (i.e., electronic devices that amplify signals) are required in optical imaging and detection systems to increase weak current signals.1 If the detector itself can produce sufficient gain, however, the sensitivity of such devices may be able to overcome the limitations that are imposed by the thermal noise of electronics. An internal amplification mechanism (i.e., impact ionization) has been used in photodetection for decades. In an avalanche photodiode—a reverse-biased p-n junction device that is operated at a voltage close to breakdown voltage,2, 3 APD—an ionization collision with the lattice—occurs when the photogenerated primary carriers acquire enough energy: see Figure 1(a). Secondary electron-hole (e-h) pairs are produced from this collision, which in turn cause additional ionization collisions as the pairs cross the depletion region (i.e., the ‘avalanche’ process). APD-based photoreceivers achieve sufficient sensitivity for fiber-optic communications. However, they require a high operation voltage (over 20V) and suffer from high excess noise with increasing gain. In devices with internal gain, interference originates mainly from shot noise that is amplified with the signal.4 The noise of these systems is best characterized by the excess noise factor (ENF), which is calculated from the fluctuation of the amplification gain. In our work, we are proposing a new internal amplification mechanism called the cycling excitation process (CEP). This process relies on the transitions involving localized states, which are formed via dopant compensation within a p-n junction diode. The Coulomb interactions that occur between energetic carriers and these localized states have stronger efficiency Figure 1. Schematic illustration of (a) the avalanche process and (b) the cycling excitation process (CEP). The former is based on impact ionization between the hot and the bound electron in the valance band. In contrast, CEP occurs as a result of the Auger process between a hot electron and an electron in the localized state in the dopant within the n-type region. Eg : Energy bandgap. 0: Primary carrier from direct photo absorption. 1: Carrier produced by Auger excitation.
在光学成像和检测系统中需要前置放大器(即放大信号的电子设备)来增强弱电信号然而,如果探测器本身能够产生足够的增益,这种装置的灵敏度可能能够克服由电子器件的热噪声所施加的限制。几十年来,一种内部放大机制(即冲击电离)已被用于光探测。在雪崩光电二极管(一种反向偏置pn结器件,工作电压接近击穿电压)中,当光产生的初级载流子获得足够的能量时,与晶格发生2,3 apd电离碰撞:见图1(a)。二次电子-空穴(e-h)对由这种碰撞产生,当电子-空穴(e-h)对穿过耗尽区(即“雪崩”过程)时,又会引起额外的电离碰撞。基于apd的光电接收器在光纤通信中具有足够的灵敏度。然而,它们需要高工作电压(超过20V),并且随着增益的增加而遭受高过量噪声。在具有内部增益的器件中,干扰主要来自随信号放大的散粒噪声这些系统的噪声最好由放大增益的波动计算得出的过量噪声因子(ENF)来表征。在我们的工作中,我们提出了一种新的内部放大机制,称为循环激励过程(CEP)。这一过程依赖于局域态的跃迁,局域态是通过p-n结二极管内的掺杂补偿形成的。高能载流子与局域态之间发生的库仑相互作用具有更强的效率(图1)。(a)雪崩过程和(b)循环激励过程(CEP)的示意图。前者是基于价带中热电子和束缚电子之间的碰撞电离。相比之下,CEP的发生是由于n型区域内掺杂中处于局域态的热电子和电子之间的俄歇过程。能量带隙。0:直接光吸收的主载体。1:由俄歇激励产生的载流子。
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引用次数: 0
Microscopic intracellular lasers tag individual cells over several generations 显微镜下的细胞内激光标记了几代的单个细胞
Pub Date : 2017-05-31 DOI: 10.1117/2.1201704.006899
M. Schubert, M. Gather
The ability to track individual cells among the trillions that are present in the human body is critical to advancing our understanding of many important biomedical questions. For example, tracking individual cells could enable us to study the function of neuronal networks, follow the inflammation response of immune cells, and unravel the way in which circulating tumor cells contribute to the formation of cancer metastasis. Among the techniques that have recently been developed to achieve single-cell resolution in tissue samples or whole animals, light sheet microscopy,1 transgenic labeling of cellular subsets,2 and genetic barcodes3 hold particular promise. However, as powerful as these methods are, they either rely critically on highly transparent samples, are strongly limited by the total number of unique cell tags, or are highly invasive. We recently developed a radically different approach to track large populations of cells over extended periods of time.4 Our method is based on tiny fluorescent plastic beads that are placed inside of each cell. These beads have diameters of about 15 m and are made of polystyrene doped with a brightly fluorescent green dye. Natural phagocytosis has proven very efficient for transferring the beads into immune cells (macrophages), where they act as microresonators (that is, they trap and amplify light by forcing it onto a circular path along the circumference of the bead).4, 5 When optically pumped, the green dye in the beads provides optical gain that leads to the emission of laser light within the living cell, thus enabling their detection. Furthermore, because the emitted laser frequency depends critically on the size of the bead, inherent size variations create unique, barcode-like laser spectra (see Figure 1) that allow the identification of Figure 1. Representative montage showing the operation of our microscopic intracellular lasers. Microlasers (green spheres) located inside live cells provide optical barcodes that can be used to identify and track individual cells within large populations of cells.
在人体中存在的数万亿细胞中追踪单个细胞的能力对于促进我们对许多重要生物医学问题的理解至关重要。例如,追踪单个细胞可以使我们研究神经元网络的功能,跟踪免疫细胞的炎症反应,并揭示循环肿瘤细胞促进癌症转移形成的方式。在最近开发的用于在组织样本或整个动物中实现单细胞分辨率的技术中,薄片显微镜、细胞亚群的转基因标记和遗传条形码具有特别的前景。然而,尽管这些方法很强大,但它们要么严重依赖于高度透明的样本,要么受到唯一细胞标签总数的强烈限制,要么是高度侵入性的。我们最近开发了一种完全不同的方法来长时间跟踪大量细胞我们的方法是基于放置在每个细胞内的微小荧光塑料珠。这些珠子直径约为15米,由掺有明亮荧光绿色染料的聚苯乙烯制成。自然吞噬作用已被证明非常有效地将珠子转移到免疫细胞(巨噬细胞)中,在那里它们充当微谐振器(也就是说,它们通过迫使光线沿着珠子的圆周进入圆形路径来捕获和放大光线)。当光泵浦时,珠子中的绿色染料提供光学增益,导致活细胞内激光的发射,从而使它们能够被检测到。此外,由于发射的激光频率严重依赖于珠的大小,固有的尺寸变化产生独特的,类似条形码的激光光谱(见图1),允许识别图1。代表性的蒙太奇显示我们的显微细胞内激光器的操作。位于活细胞内的微激光器(绿色球体)提供光学条形码,可用于识别和跟踪大量细胞中的单个细胞。
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引用次数: 0
Computationally inexpensive simulations for nanoimprint lithography 计算成本低廉的纳米压印光刻模拟
Pub Date : 2017-05-29 DOI: 10.1117/2.1201703.006887
H. Taylor
Among emerging nanopatterning techniques, nanoimprint lithography (NIL) is especially promising because the equipment required is relatively inexpensive. In NIL, a patterned template mechanically deforms a polymer film or resin on the surface of a semiconductor wafer (as shown in Figure 1) to transfer features and create an etching mask for subsequent processing. The prospect of reduced patterning costs enabled by this technique (compared with, for example, extreme-UV lithography) is particularly attractive to manufacturers of NAND flash memory, i.e., the predominant form of non-volatile memory used in electronic devices today. NAND flash memory does not require power to store data and is the key component of solidstate hard disk drives and camera memory cards. Nonetheless, to increase its adoption, it is crucial to reduce the cost per bit and, for this reason, there is an exceptionally strong incentive to reduce manufacturing costs. NIL is a promising approach for realizing a reduction in NAND flash manufacturing costs, but there are a number of associated challenges. For example, it is particularly difficult to achieve good inter-layer alignment and template lifetimes, and to minimize the pattern defectivity. Defectivity is the issue most in need of process modeling. There are two contributors to defectivity: random contributions (including particles or spatial errors in the dispensing of resin droplets onto the wafer); and systematic contributions, e.g., incomplete template-cavity filling, variation of the resin’s residual-layer thickness (between the template and the substrate), and template–resin adhesion. To ensure the successful use of NIL for fabricating NAND flash memory, it is necessary to predict any voids that may arise beneath the template after the dispensed droplets have spread Figure 1. Schematic illustration of nanoimprint lithography, using a droplet-dispensed resin.6 (1) A patterned quartz template is bowed and brought into contact with inkjet-dispensed pL-volume resin droplets on the wafer. (2) The curvature of the template is then relaxed to spread droplets and fill cavities. (3) After a dwell period (to enable residual layer homogenization), the resin is cured by UV exposure through the template.
在新兴的纳米图案技术中,纳米压印光刻(NIL)尤其有前途,因为所需的设备相对便宜。在NIL中,有图案的模板机械地使半导体晶圆表面的聚合物薄膜或树脂变形(如图1所示),以转移特征并为后续处理创建蚀刻掩模。这种技术(与极紫外光刻技术相比)降低图案成本的前景对NAND闪存制造商特别有吸引力,NAND闪存是当今电子设备中使用的主要形式的非易失性存储器。NAND闪存不需要电源来存储数据,是固态硬盘驱动器和相机存储卡的关键组件。尽管如此,为了提高其采用率,降低每比特的成本至关重要,因此,降低制造成本的动机非常强烈。NIL是实现NAND闪存制造成本降低的一种很有前途的方法,但也存在一些相关的挑战。例如,实现良好的层间对齐和模板生命周期以及最小化模式缺陷是特别困难的。缺陷是过程建模中最需要解决的问题。造成缺陷的因素有两个:随机因素(包括树脂滴在晶圆上分配时的颗粒或空间误差);系统的贡献,例如,不完整的模板腔填充,树脂的剩余层厚度的变化(在模板和基材之间),以及模板-树脂粘附。为了确保NIL成功用于制造NAND闪存,有必要预测在分配的液滴扩散后模板下可能出现的任何空隙(图1)。使用微滴分配树脂的纳米压印光刻原理图(1)将有图案的石英模板弯曲,使其与晶圆片上喷墨分配的pl体积树脂液滴接触。(2)然后放松模板的曲率以扩散液滴并填充空腔。(3)静置一段时间后(使残余层均质),通过模板进行紫外线曝光固化树脂。
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引用次数: 0
Design considerations for full-color e-paper 全彩电子纸的设计注意事项
Pub Date : 2017-05-25 DOI: 10.1117/2.1201704.006820
Bo‐Ru Yang, Yu-Cheng Wang, Li Wang
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引用次数: 2
Phase diagram for investigating the scattering properties of passive scatterers 研究被动散射体散射特性的相图
Pub Date : 2017-05-23 DOI: 10.1117/2.1201703.006854
Jeng-Yi Lee, Ray-Kuang Lee
The study of scattering (i.e., how a single receiver or scatterer responds to an external stimulus) is relevant to a wide range of subjects that are, in some way, related to wave physics (e.g., electromagnetic radiation, elastic waves, thermal diffusion, and quantum physics). Inspired by the recent developments of metamaterials and state-of-the-art nano-optical technologies, the design of functional scatterers has attracted much attention over the last decade (both experimentally and theoretically). For instance, unusual scattering states (including invisible cloaking, resonant scattering, coherent perfect absorption, superscattering, and superabsorbers) have been demonstrated when specific materials are used in the configuration of multilayered structures.1–5 Devices in which these scattering states are used have great potential for applications in biochemistry, greenenergy generation, ultrasensitive detection sensors, and optical microscopy. To obtain the exotic electromagnetic properties at a subwavelength scale, however, a variety of specific conditions need to be satisfied and a better understanding of scattering coefficients is thus required. The study of light radiation being scattered from small particles can be traced back to Lord Rayleigh’s explanation for the color of the sky.6 Furthermore, an exact solution for spherical scatterers was derived by Mie and Lorenz more than a century ago.7 This solution is valid for particles with any geometrical size, and for possible permittivity and permeability values. Nonetheless, although a basic understanding of the recently discovered unusual scattering states can be derived from existing scattering theory, a unified understanding of all these exotic states is still lacking. Figure 1. Phase diagram for a passive scatterer defined by the magnitude, jC .TE;TM/ n j, and the phase, .TE;TM/ n , of the transverse electric (TE) and transverse magnetic (TM) modes of electromagnetic radiation (where n denotes the order of the harmonic channel). The colored region represents the allowable solutions of C .TE;TM/ n and the white region represents the forbidden states for passive scatterers. The value (i.e., color) of the contours represents the normalized absorption cross section ( abs) for the TE or TM modes. : Wavelength of electromagnetic radiation.8
散射的研究(即单个接收器或散射体如何响应外部刺激)与广泛的主题相关,这些主题在某种程度上与波动物理相关(例如,电磁辐射,弹性波,热扩散和量子物理)。受最近超材料和纳米光学技术发展的启发,功能散射体的设计在过去十年中引起了广泛的关注(实验和理论)。例如,当在多层结构中使用特定材料时,已经证明了不寻常的散射状态(包括隐形斗篷,共振散射,相干完美吸收,超散射和超吸收)。利用这些散射态的器件在生物化学、绿色能源发电、超灵敏检测传感器和光学显微镜等领域具有巨大的应用潜力。然而,为了获得亚波长尺度的奇异电磁特性,需要满足各种特定条件,从而需要更好地理解散射系数。对小粒子散射的光辐射的研究可以追溯到瑞利勋爵对天空颜色的解释此外,一个多世纪以前,米氏和洛伦兹推导出了球面散射体的精确解该解适用于任何几何尺寸的颗粒,以及可能的介电常数和渗透率值。然而,尽管对最近发现的不寻常散射态的基本理解可以从现有的散射理论中推导出来,但对所有这些奇异态的统一理解仍然缺乏。图1所示。无源散射体的相位图,由电磁辐射的横向电(TE)和横向磁(TM)模式的幅度jC .TE;TM/ n j和相位.TE;TM/ n定义(其中n表示谐波通道的阶数)。彩色区域表示C . te的允许解;TM/ n,白色区域表示被动散射体的禁止态。轮廓的值(即颜色)表示TE或TM模式的归一化吸收截面(abs)。电磁辐射的波长
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引用次数: 0
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