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Waveguide Structures (waveguide + structure)

Distribution by Scientific Domains

Engineering	75%

Selected Abstracts

FDTD analysis of switching characteristics in magnetooptic functional devices using magnetostatic surface waves

ELECTRICAL ENGINEERING IN JAPAN, Issue 1 2008
Atsushi Noguchi
Abstract Collinear magnetooptic interaction with magnetostatic surface waves (MSSW) can be used for wavelength-selective switches, wavelength filters, and frequency shifters in wavelength-division-multiplexed (WDM) photonic networks and optical processing systems. The switching efficiency can be improved with a multilayer waveguide structure. To investigate the dynamic switching characteristics, the FDTD method was employed. The mode conversion between TE and TM mode was successfully demonstrated with FDTD simulation. The filtering characteristics were also evaluated. The FDTD results were compared with the result from the coupled mode theory, and good agreement was obtained. Switching of an optical pulse was also demonstrated by the FDTD method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(1): 40,47, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20501 [source]

Frequency/time-domain modelling of 3D waveguide structures by a BI-RME approach

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2002
P. Arcioni
This paper presents a full wave method for the determination of the mathematical model of a 3D waveguide structure in the form of the pole expansion in the s -plane of its generalized admittance matrix. The method is based on a boundary integral-resonant mode expansion approach. By the introduction of appropriate state-variables, the method leads to the pole expansion by solving a linear generalized eigenvalue problem, like in the well-known techniques used up to now in frequency/time domain modelling based on finite difference or finite element methods. With respect to these methods we have the advantage of a significant reduction in both memory allocation and computing time. Two examples show the accuracy of the results and the efficiency of the method. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Waveguide-enhanced scattering from thin biomolecular films

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2002
F. Pfeiffer
An X-ray diffraction experiment on multilamellar membranes incorporated into an X-ray waveguide structure is reported. In the device, the lipid bilayers are confined to one side by the silicon substrate and to the other side by an evaporated thin metal cap layer. Shining a highly brilliant X-ray beam onto the system, resonantly enhanced, precisely defined and clearly distinguishable standing-wavefield distributions (modes) are excited. The in-plane structure of the acyl chain ordering is then studied by grazing incidence diffraction under simultaneously excited modes. A significant gain in signal-to-noise ratio as well as enhanced spatial resolution can be obtained with such a setup. [source]

Miniaturized antenna using half-mode substrate integrated waveguide structure

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008
Cuilin Zhong
Abstract An X-band miniaturized antenna which uses half-mode substrate integrated waveguide structure is designed. We analyzed the electromagnetic field using the cavity model and the electromotive force method. The input impedance, simulated and experimental results of return loss, resonant frequency, and radiation patterns are presented. Its performances are as same as those of the corresponding microstrip antenna, but its size is half of the microstrip antenna. This planar structure can be integrated on the same substrate with other components such as filter and amplifier, and it can also be used to easily form antenna arrays. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3214,3218, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23911 [source]

Amplified Spontaneous Emission of Poly(ladder-type phenylene)s , The Influence of Photophysical Properties on ASE Thresholds,

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2008
Frédéric Laquai
Abstract Amplified spontaneous emission (ASE) of a series of blue-emitting poly(ladder-type phenylene)s (LPPP)s has been studied in thin film polymer waveguide structures. The chemically well-defined step-ladder polymers consist of an increasing number of bridged phenylene rings per monomer unit starting from fully arylated poly(ladder-type indenofluorene) up to poly(ladder-type pentaphenylene). The ASE characteristics of the polymers including the onset threshold values for ASE, the gain and loss coefficients as well as the photoluminescence (PL) properties, i.e., the solid state fluorescence lifetimes, decay kinetics and solid state quantum efficiencies have been studied by time-resolved PL spectroscopy. A fully arylated polyfluorene has been synthesized and its photophysical properties were compared to the step-ladder polymers. Steady-state photoinduced absorption and ultrafast transient absorption spectroscopy have been used to study excited state absorption of singlet and triplet states and polarons present in the solid state. The results demonstrate a minimum regarding the onset threshold value of ASE for a fully arylated poly(ladder-type indenofluorene) and a successive increase of the ASE threshold for the step-ladder polymers with more bridged phenylene rings. In particular, carbazole-containing step-ladder LPPPs exhibit significantly increased ASE threshold values as compared to their carbazole-free analogues due to a pronounced overlap of stimulated emission (SE) and photoinduced absorption (PA). [source]

An Organic Light-Emitting Diode with Field-Effect Electron Transport,

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2008
S. Schols
Abstract We describe an organic light-emitting diode (OLED) using field-effect to transport electrons. The device is a hybrid between a diode and a field-effect transistor. Compared to conventional OLEDs, the metallic cathode is displaced by one to several micrometers from the light-emitting zone. This micrometer-sized distance can be bridged by electrons with enhanced field-effect mobility. The device is fabricated using poly(triarylamine) (PTAA) as the hole-transport material, tris(8-hydroxyquinoline) aluminum (Alq3) doped with 4-(dicyanomethylene)-2-methyl-6-(julolindin-4-yl-vinyl)-4H-pyran (DCM2) as the active light-emitting layer, and N,N,-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13H27), as the electron-transport material. The obtained external quantum efficiencies are as high as for conventional OLEDs comprising the same materials. The quantum efficiencies of the new devices are remarkably independent of the current, up to current densities of more than 10 A cm,2. In addition, the absence of a metallic cathode covering the light-emission zone permits top-emission and could reduce optical absorption losses in waveguide structures. These properties may be useful in the future for the fabrication of solid-state high-brightness organic light sources. [source]

Frequency/time-domain modelling of 3D waveguide structures by a BI-RME approach

Propagation characteristic analysis of ridged circular waveguide using 2D finite-difference frequency-domain method

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2005
Qi Zhang
Abstract The propagation characteristics of ridged circular waveguides are analyzed by using 2D finite-difference frequency-domain (2D FDFD). Based on the 2D FDFD method in a cylindrical coordinate system, general difference formulas for the ridged circular waveguide are deduced, and modified difference formulas are built at some special points of the ridged circular waveguides. To verify the proposed method, three ridged circular waveguide structures are investigated and the numerical results are compared with available ones obtained by other research methods. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE 15, 2005. [source]

An efficient iterative method for analysis of a substrate integrated waveguide structures

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2010
Hassen Zairi
Abstract The article presents an efficient method for characterization of substrate integrated waveguide structures. Substrate integrated circuits are considered as an ensemble of conducting vias placed in a parallel-plate waveguide. The analysis is based on the wave concept formulation and the iterative resolution of two relationships between incident and reflected volume-waves. The reflection operator is expressed using Hankel functions and computed by considering the scattering from the ensemble of conducting posts. Numerical results have been obtained for substrate integrated waveguide (SIW) structures already presented in literature. Simulations obtained are compared with recent published results. A good agreement is achieved together with significant improvements both in computational time and memory requirements. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 45,48, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24825 [source]

Analysis of electromagnetic band-gap waveguide structures using body-of-revolution finite-difference time-domain method

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007
Ming-Sze Tong
Abstract Study of electromagnetic band-gap (EBG) structures has become a hot topic in computational electromagnetics. In this article, some EBG structures integrated inside a circular waveguide are studied. They are formed by a series of air-gaps within a circular dielectric-filled waveguide. A body-of-revolution finite-difference time-domain (BOR-FDTD) method is adopted for analysis of such waveguide structures, due to their axial symmetric properties. The opening ends of the waveguide are treated as a matched load using an unsplit perfectly matched layer technique. Excitations on a waveguide in BOR-FDTD are demonstrated. Numerical results of various air-gap lengths with respect to the period of separation are given, showing an interesting tendency of EBG behavior. A chirping-and-tapering technique is applied on the EBG pattern to improve the overall performance. The proposed EBG structures may be applied into antenna structures or other system for unwanted signal suppression. Results show that the BOR-FDTD offers a good alternative in analyzing axial symmetric configurations, as it offers enormous savings in computational time and memory comparing with a general 3D-FDTD algorithm. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2201,2206, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22668 [source]

Miniaturized elliptic bandpass filter using the novel coplanar double stepped impedance resonators

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2006
Suk-Hyung Jang
Abstract This paper presents the design and experimental results of the new miniaturized elliptic coplanar bandpass filter (EC BPF) using two types of double stepped impedance resonators (DSIRs) operating at a center frequency of 1.38 GHz. Miniaturization in the proposed BPF is achieved by connecting the transmission line between the middle of two SIRs contained in a single DSIR and both grounded planes. In addition, bond-wire bridges connected between both grounded planes (which are needed in various coplanar waveguide structures) are not required. The new four-pole EC-DSIR BPF shows good agreement with the simulation data obtained by full-wave EM simulations using Zeland IE3D ver. 10.06. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1059,1063, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21600 [source]

Waveguide bandpass filters for MMIC applications

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2005
L. Lalehparvar
Abstract Novel 3D multilayer waveguide structures for MMIC filter applications are proposed and examined in this paper. Periodic multilayer-waveguide resonant structures, which can be used for bandpass filters, are presented. The structure has a high Q and supports a simple fabrication process. An MMIC filter based on this proposed periodic-resonator configuration is designed at 74 GHz using the commercial software package HFSS. The simulated S -parameter responses and a photomicrograph of the fabricated monolithic dielectric filled rectangular waveguide on GaAs substrate are presented. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 471,473, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21020 [source]

Polarization of eigenmodes in laser diode waveguides on semipolar and nonpolar GaN

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1-2 2010
Jens Rass
Abstract Recent calculations of the eigenmodes in waveguides grown on semipolar GaN suggest that the optical polarization of the emitted light as well as the optical gain depends on the orientation of the resonator. Our measurements on separate confinement heterostructures on semipolar (112) and (102) GaN show that for laser resonators along the semipolar [11] and [011] directions (i.e. the projection of the c -axis onto the plane of growth) the threshold for amplified spontaneous emission is lower than for the nonpolar direction and that the stimulated emission is linearly polarized as TE mode. For the waveguide structures along the nonpolar [100] or [110] direction on the other hand, birefringence and anisotropy of the optical gain in the plane of growth leads not only to a higher threshold but alsoto a rotation of the optical polarization which is not any more TE- or TM-polarized but influenced by the ordinary and extraordinary refractive index of the material. We observe stimulated emission into a mode which is linearly polarized in extraordinarydirection nearly parallel to the c -axis. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]