Dissertation/Thesis Abstract

Localized Photoemission in Triangular Gold Antennas
by Scheffler, Christopher M., M.S., Portland State University, 2019, 95; 13808008
Abstract (Summary)

With the development of ultra-fast laser technology, several new imaging techniques have pushed optical resolution past the diffraction limit for traditional light-based optics. Advancements in lithography have enabled the straightforward creation of micron- and nanometer-sized optical devices. Exposing metal-dielectric structures to light can result in surface plasmon excitation and propagation along the transition interface, creating a surface plasmon polariton (SPP) response. Varying the materials or geometry of the structures, the plasmonic response can be tailored for a wide range of applications.

Photoemission electron microscopy (PEEM) has been used to image excitations in micron-sized plasmonic devices. With PEEM, optical responses can be characterized in detail, aiding in the development of new types of plasmonic structures and their applications. We show here that in thin, triangular gold platelets SPPs can be excited and concentrated within specific regions of the material (thickness ~50 nm); resulting in localized photoemission in areas of high electric field intensity. In this regard, the platelets behave as receiver antennas by converting the incident light into localized excitations in specific regions of the gold platelets. The excited areas can be significantly smaller than the wavelength of the incident light (λ ≤ 1 µm). By varying the wavelength of the light, the brightness of the excited spots can be changed and by varying the polarization of the light, the brightness and position can be changed, effectively switching the photoemission on or off for a specific region within the triangular gold structure.

In this work, the spatial distribution of surface plasmons and the imaging results from photoemission electron microscopy are reproduced in simulation using finite element analysis (FEA). In addition, we show that electromagnetic theory and simulation enable a detailed and quantitative analysis of the excited SPP modes, an explanation of the overall optical responses seen in PEEM images, and prediction of new results.

Indexing (document details)
Advisor: Könenkamp, Rolf
Commitee: Leung, Pui-Tak, Sánchez, Erik
School: Portland State University
Department: Physics
School Location: United States -- Oregon
Source: MAI 58/05M(E), Masters Abstracts International
Subjects: Physics, Optics
Keywords: Computer simulation, Finite element method (FEA), Gold antenna, Photoemission electron microscopy (PEEM), Surface plasmon polariton (SPP)
Publication Number: 13808008
ISBN: 978-1-392-05804-6
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