Power Absorption Efficiency in Superconducting Fiber Optical Waveguides

By using an analytical model and a finite element method, we investigate a new, very sensitive, superconducting traveling wave photodetector made by a fiber waveguide, which includes two high index layers and an active superconducting layer. A comparison with the corresponding superconducting box shaped waveguide shows that a larger width of the superconducting layer can be used to obtain single degenerate hybrid mode HE ₁₁. The real part of the propagation constants in the fiber is smaller in comparison with that of the box-shaped waveguide with similar dimensions but the imaginary part of the propagation constant and the power absorption efficiency in superconducting layer are comparable with those of the corresponding box-shaped waveguide. The confinement regimes of the light and the power absorption efficiency in superconducting layer can be optimized by only acting on the fiber geometry.     

Power Absorption Efficiency in Superconducting Box-Shaped Optical Waveguides

A very sensitive superconducting traveling wave photodetector made of a modified box-shaped waveguide, which includes two high index layers and an active superconducting layer, is studied. The optical propagation constants and the power absorption efficiency for guided modes are determined using the finite element method; the results show that by acting only on the waveguide geometry, different confinement regimes of the light in the absorption superconducting layer can be achieved and optimized.     

Efficiency of Modal Coupling between Graded-index Optical Waveguides

Abstract

The coupling efficiency between the fundamental modes of two different graded-index waveguides fabricated by ion exchange in the same glass substrate is calculated by numerical and variational methods. Waveguide parameters that allow the designer to achieve the maximum power transfer through the waveguide boundary are determined. A possible application to the design optimization of waveguide lenses is considered.     

Asymptotic Coupling Coefficients of Well-separated Single-mode Optical Waveguides

Abstract

Simple general formulae for the coupling coefficients of the fundamental modes on well-separated parallel optical waveguides are derived. The calculation merely requires accurate knowledge of the propagation constants and core fields of the modes on the individual waveguides, while the far-from-core fields need not be known. Results for coupled circular fibres are identical with the asymptotic expansions of previously derived exact coupling coefficients. Analytical expressions for the coupling coefficients between the fundamental modes on identical weakly guiding channel waveguides are obtained.     

Efficiency of Traveling-Wave Photodetectors in Superconducting Box-Shaped Metamaterial Optical Waveguides

Using finite element simulations we investigate a new, very sensitive, superconducting traveling-wave photodetector made from a modified box-shaped waveguide, which includes a high-index layer, a metamaterial layer and an active superconducting layer. The maximum of the electric field is shifted from the middle of the waveguide towards an interface which includes the active YBCO layer for an optimum imaginary part of the refractive index of the metamaterial. For some values of the refractive index of metamaterial and an optimized geometry of the waveguide, the power absorption efficiency in superconducting layer is comparable with or better than that of the plasmon–polariton optical waveguide.     

主支式排烟道中主烟道横截面尺寸的确定

高层住宅主支式排烟道的主烟道中烟气流动可看作是一维定常垂直摩擦管流。通过计算管流流动相与颗粒相的物理参数沿管程分布情况,确定了颗粒相流动情况,进而判断烟气排放情况。这受到排烟系统高度、烟道管径,及材料组成等因素的影响,通过预设排烟系统高度并保证良好排放情况,求得主烟道管径应满足的条件。这使得布设排烟道时可以找到一个较好的横截面尺寸,既满足烟气排放条件,又节约修建材料。     

聚合物光波导端面磁流变抛光工艺(英文)

光波导端面的表面质量会严重影响光波导器件的光耦合封装性能,耦合封装前必须对波导器件端面进行抛光处理.目前聚合物光波导端面主要依靠传统研磨盘进行抛光处理,该工艺工序复杂、抛光效率低已成为制约聚合物波导器件应用的瓶颈.基于聚合物光波导材料优良的加工特性,通过对比实验提出了聚合物光波导的磁流变端面抛光工艺.采用5μm、0.5μm和1μm粒径的氧化铈抛光粉分别配制研磨盘抛光液及磁流变抛光液对3 mm×3 mm聚合物光波导端面进行抛光实验,发现磁流变加工对聚合物光波导端面进行一次2 m in光栅扫描抛光就具有比传统研磨盘约3 h精、粗抛光较好的端面质量.经过白光干涉仪测量,磁流变抛光后光波导端面表面粗糙度的均方根值达到了2.6 nm,传统端面抛光端面粗糙度均方根值为128.7 nm.通过自动对准耦合平台测试,结果显示通过磁流变端面抛光的光波导的插入损耗由抛光前的32.7 dB降低到了17.8 dB.磁流变抛光方法可以对聚合物光波导端面进行快速、高性能的抛光,在光波导应用领域具有非常广阔的应用前景.     

Scaling and Optimization of MOS Optical Modulators in Nanometer SOI Waveguides

In this paper, a very accurate model of optical modulators in silicon-on-insulator technology is developed and validated using experimental results reported in literature. Using an optimized nanometer MOS structure, a significant bandwidth increase (around 45%), length decrease (around four times), and power consumption reduction (three times) with respect to the state-of-the-art have been obtained.      

Sensitivity of Traveling Wave Photodetectors in Superconducting Box-Shaped Plasmon-Polariton Optical Waveguides

A very sensitive superconducting traveling wave photodetector made of a modified box-shaped waveguide, which includes two high index layers and an active superconducting layer, is studied. The optical propagation constants and the power absorption efficiency for guided modes are determined using the finite element method; the results show that by acting only on the waveguide geometry, different confinement regimes of the light in the absorption superconducting layer can be achieved and optimized.     

级联型波导中古斯-汉欣位移的增强

前期的工作已经证明,由于共振效应和渗透深度的增加,利用毫米尺度对称金属包覆波导和自由空间耦合技术,可获得毫米量级的古斯 -汉欣(Goos-H.nchen)位移。本文在此基础上,利用一对对称金属包覆波导组成级联型结构,研究了这种结构中古斯 -汉欣位移的增强效应。实验结果表明：当激光波长变化 43 pm时,由 CCD探测器测量得到的古斯 -汉欣位移达到了 2 215 μm,约为单级波导古斯 -汉欣位移的 2倍,实验结果与理论推导完全一致。     

Optical generation of focus wave modes

Localized wave solutions of free-space wave equation can be used in numerous applications where the localized transmission of electromagnetic energy is of major importance. However, an optical implementation of localized wave fields has not been accomplished yet, except for an ultrashort version of the Bessel beams or the so called Bessel-X pulses. We propose an approach to constructing realizable optical schemes for generation of localized wave fields. We show that wavelength dispersion of the cone angle of axicons and circular diffraction gratings can be used to generate good approximation to focus wave modes.     

Performance Analysis of Linear Permanent-Magnet Motors With Finite-Element Analysis

This paper presents models for finite-element analyses and design of linear permanent-magnet motors (LPMMs) with surface-mounted or interior-buried permanent magnets (PMs). Several different models are studied in order to compare and discuss different LPMM structures. Using an analytical model of LPMMs, equations for thrust are derived. Then, we used 2-D finite-element analysis to illustrate the performance variation of LPMMs caused by the variation of structure parameters. Computer simulation results show that the characteristics and dimensions of the PMs, the shapes and dimensions of the armature, and the exciting current all have significant effects on motor performance. Several design examples based on the effects of these parameters demonstrate the design of the LPMMs. The design consideration presented in this paper can be used to determine preliminary LPMM mechanical structures before hardware implementation.     

Efficient Sub-wavelength Plasmonic Superconducting Photodetectors in Ultra-Thin Planar Waveguides and in Optical Fibers

By using a finite-element method we investigate the efficiency of sub-wavelength plasmonic superconducting photodetectors in ultra-thin planar waveguides (the incident wave is P-polarized) and in optical fibers (a traveling wave). The unit cell of a periodic sub-wavelength planar waveguide is made by a gold strip that is encapsulated in an YBCO layer and further enclosed above by an air layer and beyond by a thick gold plate substrate. For a planar structure with a single unit cell, the power absorption in YBCO layer is very large (between 0.929 and 0.975) for a fixed wavelength λ=1.55 μm when the distance between the strips and gold substrate is varied between 17 nm and 32 nm. When the wavelength is varied between 1.1 μm and 1.9 μm, the power absorption in YBCO layer is between 0.944 and 0.965 with a maximum of 0.976 at λ=1.40 μm. The superconducting traveling wave photodetector is made by an optical fiber, which includes a gold core surrounded by a number of smaller gold cylinders at a small distance from the central gold region and that are encapsulated in an active YBCO layer and further enclosed by an air layer. In our structure of the fiber with 18 smaller gold cylinders, the imaginary parts of the effective index of plasmon modes (two nondegenerate modes and eight twofold degenerate modes) and the power absorption (between 0.904 and 0.976) in active YBCO layer are very large. The first nine modes are highly confined in the YBCO layer in the space between the neighboring gold cylinders and the other nine modes are highly confined in the YBCO layer but in the space between the small gold cylinders and the gold core. Although in our structure, the thickness of the YBCO layer is 10 times smaller in comparison with that of a recently published model with 32 small gold cylinders, the losses in active YBCO layer are also very large.     

Finite-Element Analysis of Laminated Stiffened Cylindrical Shallow Shell

A finite-element solution for a geometrically nonlinear fiber composite shallow shell with Stringer-type stiffeners is presented. A laminated, anisotropic thin/thick shallow stiffened shell finite element is developed and applied for the solution of several static problems. Geometrically, a nonlinear finite-element model is based on the nonlocking shear deformable theory. Stiffened composite cylinders are subjected to mechanical loading and the shallow shell theory is used for the geometric representation and formulation of the axially stiffened cylinders. A new, two-sided meshing system is generated to represent a cylindrical shell with stiffeners in a three-dimensional coordinate system.     

Enhancement of Goos-H(a)nchen Shift with Cascade Optical Waveguides

前期的工作已经证明,由于共振效应和渗透深度的增加,利用毫米尺度对称金属包覆波导和自由空间耦合技术,可获得毫米量级的古斯-汉欣(Goos-H(a)nchen)位移.本文在此基础上,利用一对对称金属包覆波导组成级联型结构,研究了这种结构中古斯-汉欣位移的增强效应.实验结果表明:当激光波长变化43 pm时,由CCD探测器测量得到的古斯-汉欣位移达到了2 215 μm,约为单级波导古斯-汉欣位移的2倍,实验结果与理论推导完全一致.     

Absorption Efficiency of Traveling Wave Photodetectors in Superconducting Fiber Plasmon–Polariton Optical Waveguides

By using an analytical model and a finite element method, we investigate a new, very sensitive, superconducting traveling wave photodetector made by an optical fiber, which includes a high index layer (LaAlO₃) with small losses, a metallic (gold) layer, and two active superconducting layers (YBCO). While the fundamental guided degenerate mode HE₁₁ is highly confined in the interior YBCO layer, the plasmon non-degenerate mode TM₀₁ and plasmon degenerate mode HE₁₂ are tightly confined in the exterior superconducting layer. In our structure of the fiber with five layers (without a buffer layer), the imaginary parts of the HE₁₁, TM₀₁, HE₁₂ modes and the power absorption efficiency in superconducting layers are larger in comparison with that of a fundamental mode from a LaAlO₃?CYBCO?CAu planar waveguide. The confinement regimes of the light and the power absorption efficiency in superconducting layers can be optimized by only acting on the fiber geometry.     

Cointegration of Gate-All-Around MOSFETs and Local Silicon-on-Insulator Optical Waveguides on Bulk Silicon

In this work we present a bulk silicon technology platform able to cointegrate gate-all-around (GAA) MOSFETs and local SOI waveguides with pentagonal cross section. Wire diagonals of 100-800 nm are obtained using a lithographic resolution of 0.8 mum. Well-functioning triangular multigate MOSFETs are reported, and tested up to 150 degC. A significant increase is observed in the low-field mobility mu₀ for small devices (W_effles500 nm), which is attributed to local volume inversion in the corners. Preliminary characterization of the optical waveguides is carried out, showing optical losses of a few dB/cm. The processing is entirely CMOS compatible, does not require access to advanced lithography equipment, and is based on a silicon bulk substrate. Thus, this technology might serve as the basis for a low-cost, high-performance optical signaling platform     

Optical properties and photonic modes in patterned semiconductor systems

The optical response of a photonic crystal slab, where a dielectric grating is the elementary building block, is computed in the semiclassical framework, and compared with the dispersion curves of the bulk. The formalism adopted for the calculation employs the eigenmodes of a single layer as basis set for electromagnetic field expansion; it allows us to compute photonic crystal slab optical response as well as dispersion curves. Recently, the method was generalized to take into account spatial dispersion effects close to an exciton resonance of the system, and it was possible also to study the transition from dissipative to dispersive regime for a system under Bragg condition. The role of bulk and surface waves in the system is discussed as a function of the layer number N in the range N = 1 ÷ ∞. The “mirror effect”, observed in rectangular self-sustained gratings, due to the interplay among traveling, evanescent and guided waves, is recovered. This effect can be preserved also in the semi-infinite photonic crystal for selected values of the physical parameters. The role of light polarization in 1D and 2D systems is briefly discussed.