Table of Contents

Contains the table of contents

Electromagnetic Wave Theory and Applications

Contains reports on twelve research projects.Joint Services Electronics Program (Contract DAALO3-86-K-0002)National Science Foundation (Grant ECS 85-04381)National Aeronautics and Space Administration/Goddard Space Flight Center (Contract NAG5-270)National Aeronautics and Space Administration/Goddard Space Flight Center (Contract NAG5-725)U.S. Navy - Office of Naval Research (Contract N00014-83-K-0258)U.S. Navy - Office of Naval Research (Contract N00014-86-K-0533)U.S. Army - Research Office Durham (Contract DAAG29-85-K-0079)International Business Machines, Inc.National Aeronautics and Space Administration/Goddard Space Flight Center (Contract NAG5-269)Simulation TechnologiesSchlumberger-Doll Researc

Indium Antimonide Plasmonic Nanostructures for Tunable Terahertz Sources

In this work, procedures were successfully created and deployed for the development, characterization, and study of indium antimonide nanostructures as well as their terahertz plasmonic response. Using molecular beam epitaxy, indium antimonide was successfully grown on Gallium Arsenide (100) substrates of various surface misorientations. The resulting indium antimonide showed a reflection high energy electron diffraction pattern characteristic of a single-crystal epitaxial layer. These layers were then characterized through, Nomarski interference contrast microscopy, atomic force microscopy, high-resolution x-ray diffraction, and electron channeling contrast imaging. Cleaved samples from these growths were also used in developing a nanofabrication procedure to produce structures where the largest dimension was 4μm. Ultraviolet photolithography and inductively coupled plasma etching were used to shape the indium antimonide material. Electromagnetic simulations were also carried out to demonstrate the tunable response of a localized surface plasmon resonance. The localized surface plasmon resonance frequency is demonstrated to depend on the temperature of the indium antimonide. This project will serve as a stepping stone for the pathway into the development of tunable indium antimonide terahertz plasmonic devices for use in conjunction with terahertz sources

Enriched finite elements for the solution of hyperbolic PDEs

This doctoral research endeavors to reduce the computational cost involved in the solution of initial boundary value problems for the hyperbolic partial differential equation, with special functions used to enrich the solution basis for highly oscillatory solutions. The motivation for enrichment functions is derived from the fact that the typical solutions of the hyperbolic partial differential equations are wave-like in nature. To this end, the nodal coefficients of the standard finite element method are decomposed into plane waves of variable amplitudes. These plane waves form the basis for the proposed enrichment method, that are used for interpolating the solution over the elements, and thus allow for a coarse computational mesh without jeopardizing the numerical accuracy. In this research, the time dependant wave problem is established into a semi-discrete finite element formulation. Both implicit as well as explicit discretization schemes are employed for temporal integration. In either approach, the assembled system matrix needs to be inverted only at the first time step. This inverted matrix is then reused in the subsequent time steps to update the numerical solution with evolution of time. The implicit approach provides unconditional stability, whereas the explicit scheme allows lumping the mass matrix into blocks that are cheaper to invert as opposed to the consistent mass matrix. These methods are validated with several numerical examples. A comparison of the performances of the implicit and the explicit schemes, in conjunction with the enriched finite element basis, is presented. Numerical results are also compared to gauge the performance of the enriched approach against the standard polynomial based finite element approaches. Industrially relevant numerical examples are also studied to illustrate the utility of the numerical methods developed through this research