这项工作是部分被研究公司的科技进步（批准10626），美国国家科学基金会（DMR-1308084），以及旧金山州立大学的内部奖励WM支持，我们感谢我们的合作者保罗·蔡金来自纽约大学的有益的讨论实验设计和提供网络分析仪系统，让我们在SFSU在现场使用。我们感谢我们的理论合作者，高清光子带隙材料，玛丽安弗洛雷斯库，保罗·斯坦哈特和萨尔Torquato各种讨论的发明者，为我们提供了高清点模式和持续讨论的设计。

1，设计一个二维Hyperuniform无序介质结构11 <ol><li>选择2D hyperuniform障碍点图案用德劳内细分子类（蓝色圆圈图2），并对其进行分区（ 图2蓝色线）。二维德劳内镶嵌的三角测量，最大限度地形成了每个三角形的最小角度，保证有每个三角形11的外接圆内没有其他问题。 </li><li>定位每个三角形的质心（实心黑色圆圈中的图2）;这些形心是半径r 11的电介质杆的位置。 </li><li>连接相邻的三角形（ 图2中粗红线）的质心，以产生围绕每个点11的细胞。 </li><li>创建CAD设计文件与孔和槽的上杆和围墙将组装14 2厘米高的高清基础模板。使用HD模式为:a =1.33厘米平均内杆间距，设置孔半径为2.5毫米，槽的宽度，以0.38毫米。设置深度为孔和槽为1厘米深，以稳定的插杆和墙壁。 </li><li>比较14创建一个类似的CAD设计文件的结晶基础模板（方形点阵）。使用相同的晶格常数为HD结构（1.33厘米），在相同的孔半径（2.5毫米）和狭缝宽度（0.38毫米）。 </li></ol> 2，样品建设和准备<ol><li>制作模板。通过使用产生由紫外激光光聚合了坚实的塑料模型立体光刻机制造HD和正方形格子的塑料基地。使用透明的树脂，例如聚碳酸酯类塑料。的分辨率为0.1mm，在水平和垂直方向的方向。 （请参阅图3，中图）。 </li><li>准备积木:订单市售氧化铝Ř消耗臭氧层物质和薄壁切割精确的尺寸（参见图3，左图）。设置高度以不超过几个波长更小，例如10.0厘米。所有杆的直径为5.0毫米。壁厚总是0.38毫米和宽度各不相同1.0毫米至5.3毫米，0.2毫米递增。 </li><li>构建了无缺陷的测试结构的能带隙的测量。插杆和壁进入基地所需结构的架构。两个杆和墙壁上的聚合物基体的构建网络的侧视图示于图3中，右侧面板。 </li><li>设计的波导管或空腔缺陷:通过直接删除或修改杆和壁沿着设计的路径， 如图9A和9C创建通过样品的各种波导。样品的模块化设计允许点和线或曲线的缺陷的快速和容易的修改。 </li></ol> 3，主要仪器<ol><li>使用合成的清扫车（微波发生器）提供微波炉与45兆赫的频率覆盖范围为50 GHz的精确1Hz的频率分辨率。在发电机连接到S-参数测试装置来测量两个端口（终端）之间的传输参数。使用通用接口总线（GPIB）链接和电缆清扫和测试集之间的通信。 </li><li>用微波矢量网络分析仪（VNA）来处理从S-参数接收的信号测试 - 设置和测量信号的幅度和相位。置的S参数测试设定为S21模式使得VNA的输出包含检测到的电场的实分量和虚分量在端口1与端口2相对于源极信号作为频率的函数的数据文件</li></ol> 4，仪器设置<ol><li>开始/结束频率。选择的频率范围的适当的开始和结束值使用VNA我们测量呃菜单。与光子带隙相关的有关的频率范围取决于样品的晶格间距的电介质索引上。使用7 GHz到15 GHz的微波对氧化铝样品的晶格间距为1.33公分。 </li><li>平均因子。矢量分析仪计算基于多个测量值的平均值，以减少随机噪声的每个数据点。通过输入矢量网络分析仪面板上所需的多种选择，以4,096为512的平均因子。选择较高的平均因子，以尽量减少噪音，并选择一个较低的平均系数为更快的扫描。 </li><li>点数。在7千兆赫至15千兆赫范围内的测量，选择的数据点（801）的最大数目，VNA的屏幕上的菜单上，以实现10 MHz的频率分辨率。 </li><li>校准。校准系统通过直接测量的相对透射率，并具有相同的背景和无角antenn之间的样本归一化其对一个预先校准的设置的发送作为。通过这样做，由于电缆，适配器，波导和天线的所有背景损耗可以被消除，和有和没有试验样品的相对透射率被直接记录。 <ol><li>对于带隙的测量，测量经过的角之间的自由空间中的微波传输彼此面对以28的距离，并将结果保存为校准在VNA的设定。在采集数据的实际实验与角之间的结构，打开校准选择"校准开"矢量网络分析仪的显示器上进行设置。通过矢量网络分析仪计算出的数据将是针对校准组自动归一化，并返回发送功率之比具有和不具有代替样品。 </li><li>对于波导的测量，一个有意义的校准未明确定义的，由于通过样品波导的传输可以很容易地超过在自由空间中的两个角之间的校准传输。开启关上的VNA校准监视和记录的原始传输，它是在源信号的检测信号。将喇叭旁边的波导通道的开口，以达到最佳耦合效率。 </li></ol></li></ol> 5，实验装置<ol><li>配置在图4所示的实验装置，使用高品质的半柔性同轴电缆与输入/输出波导连接的S参数测试设置端口。连接的角锥喇叭天线，通过矩形单模波导和适配器端口，以确保辐射是线偏振光，该电场从喇叭的辐射平行于喇叭的短边。 </li><li>对于带隙测量:遵循以下步骤来测量通过无缺陷的样品传输到泛北部湾表征缺陷的免费样品。 <ol><li>对齐的角垂直和水平方向彼此面对。排列轰orns在足够远的距离，平均波长，比如20倍，从而使远场辐射到达样品可近似为平面波。校准中的自由空间相面对的角之间的传输未经测试样品，并将其存储在校准存储器。 </li><li>放置在两个相对的角之间作出杆和墙壁上的旋转台的无缺陷结构。打开在步骤5.2.1记录到VNA存储器的校准集。该系统现在可以测量通过归一对校准存储器的发送功率的样品的相对透射率。 </li></ol></li><li>波导和空洞缺陷的测量:坚持以设置实验的步骤如下: <ol><li>通过去除或替换杆和墙壁中的无缺陷结构， 如图9A和9C构建各种波导和空腔。 </li><li>安排角尽可能靠近通道开口尽可能以确保良好的耦合到信道。对于弯曲和弯曲通道居中的角与平行于所述开口的边缘的通道的中间。 </li><li>关闭校准。现在，矢量网络分析仪系统已准备就绪，以测量和端口1记录检测到的功率的原始传输率在端口2上的源动力。 </li></ol></li></ol> 6，数据采集与分析<ol><li>定性的角度的样品的光子性质的依赖性: <ol><li>地方结构在两个相对的角之间作出杆和墙壁的一个近圆形边界上的旋转舞台。 </li><li>确保保存在VNA的存储器中的校准被接通，在步骤5.2.2。零上，通过结构的旋转台和测量传输的角度刻度。在零入射角的初始计量后，旋转样品和测量等角度INCREM传输需求测试，例如每2°至180°的旋转为止。 </li></ol></li><li>表征极化光子特性的样品的依赖: 执行在两个分别不同的偏振如上所述，通过改变喇叭开口方向的所有测量。对于TM偏振，设置角"短边（E场方向）垂直于所述样品基体并平行于杆的水平面上。对于TE偏振，旋转角90度，使得它们的短边（E场方向）是在水平平面内。 </li><li>表征各种波导通道:确保校准步骤5.3.3关闭。放置的角旁的样品为最佳耦合。测量通过去除和/或更换杆和壁沿着通道路径构造的各种信道的传输。同时监控在VNA的实时传输信号，修改通过广告中的信道路径定并除去多余杆和壁的优化的传输功率或所希望的滤波带宽。 </li><li>进行类似的测量类似于上面描述的正方形格子光子晶体什么的比较。 </li><li>数据分析。分析和图形使用计算机程序，如MATLAB中的数据。积测量传输作为一个函数频率（线图），如图5，图2，图9B和9D来研究通过将样品或传输通不过的波导通道的权宜之计。积传输作为频率和角度（彩色等高线图）的函数来分析结构和它们的角度依存性的阻带内的特性， 如图6和图7所示 。 </li><li>该协议建议通过样品展示实测传输，频率和入射角极coordi功能止数据12，以直接可视化的旋转对称性和角光子性质的依赖性。生成的极坐标图来直接显示晶体结构的布里渊区的边界，并揭示PBG形成和布拉格散射面（布里渊区边界）的晶体和准晶之间的关系。 </li></ol>

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从hyperuniform无序点图案开始，2D HD的结构包括杆和/或壁的网络可以被设计，以获得一个完整的带隙为所有极化11。根据设计，构建与孔和槽装配2D氧化铝杆和墙壁结构在厘米级这可能与微波测试的模板。我们选择了微波炉的工作，因为厘米尺度的构建块，诸如氧化铝棒和墙壁，价格便宜，并且易于处理。我们已通过实验证明了在第一次，它可以具有在二维hyperuniform无序结构的各向同性完全?...

带隙的光子的存在，一直是许多科学著作的焦点，从早期的研究由瑞利勋爵在一维的阻带，一个范围，从传播通过定期介质1禁止频率进行首发。研究在周期性结构的电磁波（EM）的传播，确实盛行于E. Yablonovitch 2,3和S.约翰福音4的开创性的出版物后，在过去二十年。所谓"光子晶体"被创造出来了Yablonovitch描述周期性介电结构是具有光子带隙（PBG）。 光子晶体是周期性介电结构，拥有独立的平移对称性，在周期性的方向使它们不变下的翻译。当这个周期相匹配传入的电磁（EM）波的波长，波段Ø˚F频率变高衰减，可能会停止传播。如果够宽，禁频率的范围，也被称为阻带内，可能会重叠，全方位地打造泛北部湾，禁止某些频率的光子的存在。 在概念上，在光子晶体中的EM波传播是类似于电子波传播中的半导体材料，其具有电子能量，也被称为带隙的禁止区域。类似的工程师们采用半导体控制和修改电子通过半导体的流动方式，可以用于需要光控制各种应用的带隙的材料。例如，光子带隙材料可以限制光的波长大小的腔特定的频率，引导或过滤光线沿着他们5线缺陷。是建议PBG材料中使用，用于控制在电信6的光的应用流，7激光器，光学电路和光计算8，与太阳能收集9。 一种二维（2D）方形晶格光子晶体具有4倍的旋转对称性。在不同的入射角进入晶体的电磁波（例如，0°和45°相对于晶面）将面对不同的周期性。布拉格散射在不同的方向引出阻止不同的波长，可能不会在所有方向上重叠而形成光子带隙的频带，没有材料的非常高的折射率对比。此外，在2D结构中，两个不同的电磁波的极化，横向电场（TE）与横向磁场（TM），往往形成带隙在不同的频率，使得它更难以形成一个完整的带隙在全部极化5四面八方。在周期性结构中，旋转对称的有限选择导致本征异向性（安古拉ř依赖性），这不仅使得它很难形成一个完整的带隙，而且还大大地限制了功能性缺陷的设计自由度。例如，波导的设计已被证明在光子晶体10被限制沿主要对称方向非常有限的选择。 启发超越，由于周期性这些限制，大量的研究，在过去20年非常规的光子带隙材料已经完成。最近提出了一类新的无序材料具备各向同性完全光子带隙在没有周期性或准周期:在hyperuniform症（HD）的PBG结构11。光子带没有乱结构的精确解析解。的无序结构的光子性质的理论研究仅限于费时数值模拟。来计算频带，在模拟需要采用一种超小区的近似方法和阿瓦伊拉布勒计算能力可能限制了超小区的有限尺寸。通过这些结构计算传输，计算机模拟常常假定理想的条件和像源和检测器，实际的入射电磁波轮廓之间的耦合从而忽视的实际问题，并且对准的缺陷12。此外，模拟结构的任何修改（设计缺陷），则需要新一轮的模拟。由于对超小区内的最小意义的大尺寸，这是很乏味和不切实际的，系统地研究各种缺陷的设计架构，这些无序材料。 我们可以通过研究无序光子结构实验避开这些计算问题。通过我们的实验中，我们能够验证在HD的结构的完全光子带隙的存在。使用微波实验，我们还可以得到相位信息和显示字段配线架在他们现有的光子态的分销和分散性能。使用易于修改和模块化样品在厘米级，我们所用的无序系统测试各种波导和空腔（缺陷）的设计和分析PBGs的鲁棒性。这种复杂的无序光子结构的分析或者是不实际或不可能获得通过数值和理论研究。 在设计过程中首先选择了"隐身"hyperuniform点模式13。 Hyperuniform点图案是系统中的各点的内半径为R的"球形"采样窗口的数目方差，生长速度比窗口体积大的R，即，速度比R D所中的d尺寸。例如，在二维泊松随机分布的点图案，在域ŕ点的数量的方差正比于R &lt;SUP&gt; 2。然而，在hyperuniform障碍点模式，在半径为R的一个窗口点的差异，正比于R， 图1显示了一个hyperuniform无序点图案和泊松点图案11之间的比较。我们使用的hyperuniform无序点模式的子类被称为"隐身"11。 使用弗洛雷斯库等 11所描述的设计方案，我们构建了介电墙和棒的网络，造就了2D hyperuniform介质结构类似于晶体，但没有固有的周期性和各向同性的限制。墙上的网络有利于TE偏振带隙，而棒最好形成带隙和TM偏振。一种模块化设计，开发，使得样品可以容易地修改为具有不同极化和introd使用ucing自由波导和空洞缺陷。由于麦克斯韦方程组的标度不变性，在微波领域中观察到的电磁特性可以直接适用于红外和光学制度，其中，样品将被缩放以微米和亚微米尺寸。

<table><tbody><tr><td>Stereolithography machine</td><td>3D Systems</td><td>SLA-7000</td><td></td></tr><tr><td>Resin for base</td><td>3D Systems</td><td>Accura 60</td><td></td></tr><tr><td>Alumina rods</td><td></td><td></td><td>r=2.5 mm, cut to 10.0 cm height</td></tr><tr><td>Alumina sheets</td><td></td><td></td><td>Thickness 0.38 mm, various width: from 1.0 mm to 5.3 mm with 0.2 mm increments</td></tr><tr><td>Microwave generator</td><td>Agilent/HP</td><td>83651B</td><td></td></tr><tr><td>S-Parameter test set</td><td>Agilent/HP</td><td>8517B</td><td></td></tr><tr><td>Microwave Vector Network Analyzer</td><td>Agilent/HP</td><td>8510C</td><td></td></tr></tbody></table>

using microwave and macroscopic samples of dielectric solids to study the photonic properties of disordered photonic bandgap materials

最近，无序光子材料已被建议作为一种替代周期性晶体的完全光子带隙（PBG）的形成。在这篇文章中，我们将介绍这些方法构建和表征使用微波炉宏观无序光子结构。微波政权提供了构建和测试PBG媒体最方便的实验样本量。容易被操纵晶格介质成分在建设各种2D结构上预印塑料模板顶部延伸的灵活性。一旦建成，该结构可以迅速修改了点和线的缺陷，使自由波导和过滤器。测试是采用广泛使用矢量网络分析仪和对微波喇叭天线。由于电磁场的尺度不变性，我们在微波区域中获得的结果可以直接应用到红外线和光学区域。我们的方法很简单，但提供EXCI挺新的洞察光线和无序物质相互作用的性质。 我们的代表性成果包括二维（2D）hyperuniform无序介质结构的第一个实验演示一个完整的和各向同性光子带隙的存在。此外，我们通过实验证明这种新型光子结构通过任意形状的自由波导引导电磁波（EM）的能力。

我们已经取得了有史以来的各向同性完全光子带隙存在于hyperuniform症介质结构的第一个确认。在这里，我们提出我们的HD结构的结果，并把它们比作一个周期性正方晶格光子晶体。 图5显示了TE偏振传输（DB）与频率（GHz）的hyperuniform疾病结构在同一入射角的半对数图。这个曲线图表明，在阻带区域8.5和9.5千兆赫，其中透射强度下降幅度超过两个数量级之间大致位?...

Watch this Scientific Journal Video about Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials at JoVE.com

Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

无序的结构提供了功能性缺陷的设计形成光子带隙和前所未有的自由的新机制。规避无序系统中的计算，我们构建新的类PBG材料的模块化宏观样品，并使用微波来表征它们的尺度不变光子性质，以简单且廉价的方式。

利用微波和电介质固体的宏观样本，研究无序光子带隙材料的光子特性

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). ...

using-microwave-macroscopic-samples-dielectric-solids-to-study

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

12.2K 次观看.  San Francisco State University. 无序的结构提供了功能性缺陷的设计形成光子带隙和前所未有的自由的新机制。规避无序系统中的计算，我们构建新的类PBG材料的模块化宏观样品，并使用微波来表征它们的尺度不变光子性质，以简单且廉价的方式。 

视频: Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view and for its considerable potential for practical applications. Slow light photonic crystal waveguides, in particular, have played a major part and have been successfully employed for delaying optical signals1-4 and the enhancement of both linear5-7 and nonlinear devices.8-11
Photonic crystal cavities achieve similar effects to that of slow light waveguides, but over a reduced band-width. These cavities offer high Q-factor/volume ratio, for the realization of optically12 and electrically13 pumped ultra-low threshold lasers and the enhancement of nonlinear effects.14-16 Furthermore, passive filters17 and modulators18-19 have been demonstrated, exhibiting ultra-narrow line-width, high free-spectral range and record values of low energy consumption.
To attain these exciting results, a robust repeatable fabrication protocol must be developed. In this paper we take an in-depth look at our fabrication protocol which employs electron-beam lithography for the definition of photonic crystal patterns and uses wet and dry etching techniques. Our optimised fabrication recipe results in photonic crystals that do not suffer from vertical asymmetry and exhibit very good edge-wall roughness. We discuss the results of varying the etching parameters and the detrimental effects that they can have on a device, leading to a diagnostic route that can be taken to identify and eliminate similar issues.
The key to evaluating slow light waveguides is the passive characterization of transmission and group index spectra. Various methods have been reported, most notably resolving the Fabry-Perot fringes of the transmission spectrum20-21 and interferometric techniques.22-25 Here, we describe a direct, broadband measurement technique combining spectral interferometry with Fourier transform analysis.26 Our method stands out for its simplicity and power, as we can characterise a bare photonic crystal with access waveguides, without need for on-chip interference components, and the setup only consists of a Mach-Zehnder interferometer, with no need for moving parts and delay scans.
When characterising photonic crystal cavities, techniques involving internal sources21 or external waveguides directly coupled to the cavity27 impact on the performance of the cavity itself, thereby distorting the measurement. Here, we describe a novel and non-intrusive technique that makes use of a cross-polarised probe beam and is known as resonant scattering (RS), where the probe is coupled out-of plane into the cavity through an objective. The technique was first demonstrated by McCutcheon et al.28 and further developed by Galli et al.29

Use of photonic crystal slow light waveguides and cavities has been widely adopted by the photonics community in many differing applications. Therefore fabrication and characterization of these devices are of great interest. This paper outlines our fabrication technique and two optical characterization methods, namely: interferometric (waveguides) and resonant scattering (cavities).

光子晶体慢光波导和腔体的制备与表征

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view ...

科研

工程学

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency.

The customized techniques developed in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators are presented. The protocols to obtain and characterize these resonators are detailed, and an explanation of some of their applications in microwave photonics is given.

基于微波光子系统回音壁模式谐振器

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various ...

Fabrication and Characterization of Disordered Polymer Optical Fibers for Transverse Anderson Localization of Light

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed polymer optical fiber is composed of 80,000 strands of poly (methyl methacrylate) (PMMA) and polystyrene (PS) that are randomly mixed and drawn into a square cross section optical fiber with a side width of 250 &mu;m. Initially, each strand is 200 &mu;m in diameter and 8-inches long. During the mixing process of the original fiber strands, the fibers cross over each other; however, a large draw ratio guarantees that the refractive index profile is invariant along the length of the fiber for several tens of centimeters. The large refractive index difference of 0.1 between the disordered sites results in a small localized beam radius that is comparable to the beam radius of conventional optical fibers. The input light is launched from a standard single mode optical fiber using the butt-coupling method and the near-field output beam from the disordered fiber is imaged using a 40X objective and a CCD camera. The output beam diameter agrees well with the expected results from the numerical simulations. The disordered optical fiber presented in this work is the first device-level implementation of 2D Anderson localization, and can potentially be used for image transport and short-haul optical communication systems.

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. This microstructured fiber can transport a small localized beam with a radius that is comparable to the beam radius of conventional optical fibers.

无序横向安德森本地化光聚合物光纤的制备和表征

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed ...

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we demonstrate an optical spectroscopy method that is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots (QDs) using a standard, easy-to-use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser line-width limited resolution with multi-channel photoluminescence detection. Such a scheme allows for considerable improvement of resolution over that of a common single-stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonon&#39;s energy difference allows one to separate and filter out the laser light exciting the quantum dot. An advantageous feature of this method is its straight forward integration into standard spectroscopy setups, which are accessible to most researchers.

The manuscript describes a method of phonon-assisted quasi-resonant fluorescence spectroscopy that incorporates both laser-limited resolution and photoluminescence (PL) spectroscopy. This method utilizes optical phonons to provide linewidth-limited resolution spectra of atom-like semiconductor structures in the energy domain. The method is also easily realized with a single spectrometer optical spectroscopy setup.

高分辨率声子辅助准共振荧光光谱仪

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we ...

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using femtosecond laser-induced ablation.

1-D光子晶体空穴对纳米纤维使用飞秒激光诱导消融制造

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using ...

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

通过时间分辨微波电导率重组动力学薄膜光伏材料

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

合成纳米碳和二氧化硅矩阵的表面性能

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

化学

Carrier Lifetime Measurements in Semiconductors through the Microwave Photoconductivity Decay Method

This work presents a protocol employing the microwave photoconductivity decay (&#956;-PCD) for measurement of the carrier lifetime in semiconductor materials, especially SiC. In principle, excess carriers in the semiconductor generated via excitation recombine with time and, subsequently, return to the equilibrium state. The time constant of this recombination is known as the carrier lifetime, an important parameter in semiconductor materials and devices that requires a noncontact and nondestructive measurement ideally achieved by the &#956;-PCD. During irradiation of a sample, a part of the microwave is reflected by the semiconductor sample. Microwave reflectance depends on the sample conductivity, which is attributed to the carriers. Therefore, the time decay of excess carriers can be observed through detection of the reflected microwave intensity, whose decay curve can be analyzed for estimation of the carrier lifetime. Results confirm the suitability of the &#956;-PCD protocol in measuring the carrier lifetime in semiconductor materials and devices.

As one of the important physical parameters in semiconductors, carrier lifetime is measured herein via a protocol employing the microwave photoconductivity decay method.

微波导光衰减法测量半导体中的载波寿命

This work presents a protocol employing the microwave photoconductivity decay (&#956;-PCD) for measurement of the carrier lifetime in semiconductor ...

Spectral and Angle-Resolved Magneto-Optical Characterization of Photonic Nanostructures

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by local enhancement of electric field intensity that strengthens light-matter interactions, enabling applications such as surface-enhanced Raman scattering (SERS) and surface plasmon enhanced sensing. In the presence of magneto-optically active materials, the local field enhancement gives rise to anomalous magneto-optical activity. Typically, the confined modes of a given photonic crystal depend strongly on the wavelength and incidence angle of the incident electromagnetic radiation. Thus, spectral and angular-resolved measurements are needed to fully identify them as well as to establish their relationship with the magneto-optical activity of the crystal. In this article, we describe how to use a Fourier-plane (back focal plane) microscope to characterize magneto-optically active samples. As a model system, here we use a plasmonic grating built out of magneto-optically active Au/Co/Au multilayer. In the experiments, we apply a magnetic field on the grating in situ and measure its reciprocal space response, obtaining the magneto-optical response of the grating over a range of wavelengths and incident angles. This information enables us to build a complete map of the plasmonic band structure of the grating and the angle and wavelength dependent magneto-optical activity. These two images allow us to pinpoint the effect that the plasmon resonances have on the magneto-optical response of the grating. The relatively small magnitude of magneto-optical effects requires a careful treatment of the acquired optical signals. To this end, an image processing protocol for obtaining magneto-optical response from the acquired raw data is laid out.

Photonic band structure enables understanding how confined electromagnetic modes propagate within a photonic crystal. In photonic crystals that incorporate magnetic elements, such confined and resonant optical modes are accompanied by enhanced and modified magneto-optical activity. We describe a measurement procedure to extract the magneto-optical band structure by Fourier space microscopy.

光子纳米结构的光谱和角度解析磁-光学特性

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by ...

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids

Rational design of disordered molecular aggregates and solids for optoelectronic applications relies on our ability to predict the properties of such materials using theoretical and computational methods. However, large molecular systems where disorder is too significant to be considered in the perturbative limit cannot be described using either first principles quantum chemistry or band theory. Multiscale modeling is a promising approach to understanding and optimizing the optoelectronic properties of such systems. It uses first-principles quantum chemical methods to calculate the properties of individual molecules, then constructs model Hamiltonians of molecular aggregates or bulk materials based on these calculations. In this paper, we present a protocol for constructing a tight-binding Hamiltonian that represents the excited states of a molecular material in the basis of Frenckel excitons: electron-hole pairs that are localized on individual molecules that make up the material. The Hamiltonian parametrization proposed here accounts for excitonic couplings between molecules, as well as for electrostatic polarization of the electron density on a molecule by the charge distribution on surrounding molecules. Such model Hamiltonians can be used to calculate optical absorption spectra and other optoelectronic properties of molecular aggregates and solids.

Here, we present a protocol for parametrizing a tight-binding excitonic Hamiltonian for calculating optical absorption spectra and optoelectronic properties of molecular materials from first-principles quantum chemical calculations.

用于计算分子聚合和固体光学吸收光谱和光电特性的外化学汉密尔顿

Rational design of disordered molecular aggregates and solids for optoelectronic applications relies on our ability to predict the properties of such ...