Finite element analysis of slotline-bowtie junction.

by Chong Man Yuen.Thesis (M.Phil.)--Chinese University of Hong Kong, 1997.Includes bibliographical references (leaves 125-128).DedicationAcknowledgementsList of FigureList of TableList of AppendixChapter 1. --- IntroductionChapter 1.1 --- BackgroundChapter 1.2 --- Ultra-Wide Band AntennaChapter 1.3 --- Finite Element Method (FEM)Chapter 1.3.1 --- Domain DiscretizationChapter 1.3.2 --- Formulation of Variational MethodChapter 2 --- TheoryChapter 2.1 --- Variational principles for electromagneticsChapter 2.1.1 --- Construction of FunctionalChapter 2.2 --- Artificial BoundaryChapter 2.2.1 --- Absorbing Boundary ConditionsChapter 2.2.2 --- Perfectly Matched Layer (PML)Chapter 2.3 --- Edge Basis FunctionChapter 2.4 --- Slotline AnalysisChapter 3 --- Implementation of FEMChapter 3.1 --- Formulation of Element matrixChapter 3.2 --- Mesh GenerationChapter 3.3 --- AssemblyChapter 3.4 --- Incorporation of Boundary ConditionsChapter 3.5 --- Code ImplementationChapter 4 --- Finite Element SimulationsChapter 4.1 --- SlotlineChapter 4.2 --- Artificial Boundary of the domainChapter 4.3 --- Slotline Taper JunctionChapter 4.4 --- Slotline Bowtie JunctionChapter 5 --- ConclusionAppendix A1Appendix A2Appendix A3Bibliograph

Characterisation of silicon photonics devices

Silicon based integrated circuits has been dominating the electronics technology industry in the last few decades. As the telecommunications and the computing industry slowly converges together, the need for a material to build photonics integrated circuits (PIC) that can be cost-effective and be produced in mass market has become very important. This thesis describes and outlines the characteristics of high index contrast waveguides as a building blocks that can be designed, fabricated and employed on devices in silicon photonics. Initially in this work, a fully vectorial H-field based finite element method has been used to obtain the modal characteristics of high index contrast bent waveguide to get a better understanding of the curved section. Through the beam propagation method, the propagation losses and the spot-size along the propagation distance are obtained when a mode from the straight guide is launched into a bent guide. It is also learnt that mode beating exists at the junction of a straight-to-bent waveguide, in which higher order modes will also be generated. It will be shown in this work that power do exchange between the two polarization states, therefore the polarization conversion, the power losses and the bending losses will be investigated. It will also shown in here that by applying lateral offsets with coupled waveguides of unequal widths, the insertion loss can be reduced. Secondly, for a high index contrast waveguide such as the silicon strip waveguide with a nanoscale cross-section, modes in such waveguide are not purely TE or TM but hybrid in nature, with all the six components of their E and H-fields being present. Therefore a detail analysis of the modal field profiles along with the Poynting vector profile will be shown. The effects of waveguide's width and height on the effective indices, the hybridness, the modal effective area and the power confinement in the core or cladding has been studied. Furthermore the modal birefringence of such strip waveguide will be shown. It will be presented that for a strip waveguide with height of 260 nm, single mode exists in the region of the width being 200 nm to 400 nm and that the modal effective is at its minimum when width is around 320 nm for both polarization states. Thirdly, a compact polarization rotator with an asymmetric waveguide structure design, suitable for fabrication that does not require a slanted side wall or curved waveguide is considered in this work. It will be shown in here that due to the hybrid nature of the asymmetric waveguide design, maximum polarization rotation (from TE to TM) will be achieve by enhancing the non-dominant field profile of both polarized fundamental mode. As the modal hybridness and the propagation constants of both polarized modes will be obtained, the half-beat length, polarization conversion and polarization cross-talk will be calculated by using the FEM and the least squares residual boundary method (LSBR). It is learnt that a compact single stage polarization rotator with a device length of 48 μm with more than 99% of polarization conversion is achieved in this work. Finally, a study of vertical and horizontal slot waveguide will be shown. Based on silicon strip waveguide, a detail modal characteristics of E and H-fields along with the Poynting vectors are presented. It will be shown that for slot waveguide, high power confinement and power density will be achieved in the slot area. It will be presented that by optimising the waveguide and slot dimension, the performance of the power confinement and power density in the slot region can be improved

Using the method of moments and Robin Hood method to solve electromagnetic scattering problems

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 67-69).This thesis project was to write a program in C++ that solves electromagnetic scattering problems for arbitrarily shaped scatterers. This was implemented by using a surface integral formulation of Maxwell's equations, which discretizes the surface of the scatterer into thousands of triangles. The method of moments (MoM) was applied, which calculates the Green's functions between each triangle element. A matrix equation is obtained and solved using the Robin Hood (RH) method. The solution to this equation gives the scattered electromangetic field. This program is first tested on a sphere, which is compared to the analytic solution known as Mie scattering. Once these results are confirmed, the program can be used for the KATRIN experiment to ensure that no Penning traps occur in the electron spectrometer.by David A. Chester.S.B

Characterisation of silicon photonics devices

Silicon based integrated circuits has been dominating the electronics technology industry in the last few decades. As the telecommunications and the computing industry slowly converges together, the need for a material to build photonics integrated circuits (PIC) that can be cost-effective and be produced in mass market has become very important. This thesis describes and outlines the characteristics of high index contrast waveguides as a building blocks that can be designed, fabricated and employed on devices in silicon photonics. Initially in this work, a fully vectorial H-field based finite element method has been used to obtain the modal characteristics of high index contrast bent waveguide to get a better understanding of the curved section. Through the beam propagation method, the propagation losses and the spot-size along the propagation distance are obtained when a mode from the straight guide is launched into a bent guide. It is also learnt that mode beating exists at the junction of a straight-to-bent waveguide, in which higher order modes will also be generated. It will be shown in this work that power do exchange between the two polarization states, therefore the polarization conversion, the power losses and the bending losses will be investigated. It will also shown in here that by applying lateral offsets with coupled waveguides of unequal widths, the insertion loss can be reduced. Secondly, for a high index contrast waveguide such as the silicon strip waveguide with a nanoscale cross-section, modes in such waveguide are not purely TE or TM but hybrid in nature, with all the six components of their E and H-fields being present. Therefore a detail analysis of the modal field profiles along with the Poynting vector profile will be shown. The effects of waveguide's width and height on the effective indices, the hybridness, the modal effective area and the power confinement in the core or cladding has been studied. Furthermore the modal birefringence of such strip waveguide will be shown. It will be presented that for a strip waveguide with height of 260 nm, single mode exists in the region of the width being 200 nm to 400 nm and that the modal effective is at its minimum when width is around 320 nm for both polarization states. Thirdly, a compact polarization rotator with an asymmetric waveguide structure design, suitable for fabrication that does not require a slanted side wall or curved waveguide is considered in this work. It will be shown in here that due to the hybrid nature of the asymmetric waveguide design, maximum polarization rotation (from TE to TM) will be achieve by enhancing the non-dominant field profile of both polarized fundamental mode. As the modal hybridness and the propagation constants of both polarized modes will be obtained, the half-beat length, polarization conversion and polarization cross-talk will be calculated by using the FEM and the least squares residual boundary method (LSBR). It is learnt that a compact single stage polarization rotator with a device length of 48 μm with more than 99% of polarization conversion is achieved in this work. Finally, a study of vertical and horizontal slot waveguide will be shown. Based on silicon strip waveguide, a detail modal characteristics of E and H-fields along with the Poynting vectors are presented. It will be shown that for slot waveguide, high power confinement and power density will be achieved in the slot area. It will be presented that by optimising the waveguide and slot dimension, the performance of the power confinement and power density in the slot region can be improved.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Modelling of photonic components based on ÷(3)nonlinear photonic crystals

En esta tesis se llevó a cabo un estudio de diversas propiedades de los cristales fotónicos 1D y 2D no lineales de tercer orden y de cómo se pueden aplicar dichas propiedades al desarrollo de dispositivos totalmente ópticos (por ejemplo, limitadores y conmutadores, compuertas lógicas, transistores ópticos, etc.). Se propuso una aproximación numérica para calcular las características básicas de los cristales fotónicos no lineales como, por ejemplo, el diagrama de bandas o la transmisión. La aproximación numérica presentada en la tesis tiene ciertas ventajas útiles para cualquiera que diseñe dispositivos ópticos basados en cristales fotónicos no lineales. El sofware desarrollado a base de esta aproximación numérica ha permitido diseñar y simular numéricamente un conmutador totalmente óptico cuyas prestaciones son superiores a las de dispositivos optoelectrónicos convencionales.This dissertation represents a summary of a study of different properties of 1D and 2D third-order nonlinear photonic crystals. It is shown how these properties can be utilized to develop various all-optical devices (e.g. optical limiters and switches, logical gates, optical transistors, etc.) In the dissertation, a novel numerical approximation has been proposed for analyzing the basic characteristics of the nonlinear photonic crystals like dispersion characteristics or transmittance curves. This numerical approximation possesses some important advantages useful in designing all-optical devices based on nonlinear photonic crystals. The software based on its algorithm has allowed to design and simulate a high-production all-optical switching device