Nanoscale Light Confinement:: Bowtie Antenna and Perfect Absorbers

76 Pages·2014·1.97 MB·English

UC San Diego
UC San Diego Electronic Theses and Dissertations
Title
Nanoscale Light Confinement : : Bowtie Antenna and Perfect Absorbers
Permalink
https://escholarship.org/uc/item/4cb7g8qv
Author
Rosen, David Alexander
Publication Date
2014

Peer reviewed|Thesis/dissertation
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University of California
UNIVERSITY OF CALIFORNIA, SAN DIEGO

Nanoscale Light Confinement: Bowtie Antenna and Perfect Absorbers

A Thesis submitted in partial satisfaction of the requirements for the degree Masters of
Science

In

NanoEngineering

by

David Alexander Rosen

Committee in charge:

Professor Andrea Tao, Chair
Professor Eric Fullerton
Professor Donald Sirbuly

2014
Copyright
David Alexander Rosen, 2014
All rights reserved.
SIGNATURE PAGE

The Thesis of David Alexander Rosen is approved and it is acceptable in the quality and
form for publication on microfilm and electronically:

Chair

University of California, San Diego

2014

iii
DEDICATION

Dedicated to my mother and father for always supporting me, and to my brother for all of
his help in all aspects of life.

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TABLE OF CONTENTS
SIGNATURE PAGE ......................................................................................................... iii
DEDICATION ................................................................................................................... iv
TABLE OF CONTENTS .................................................................................................... v
LIST OF FIGURES .......................................................................................................... vii
LIST OF SCHEMES.......................................................................................................... ix
ACKNOWLEDGEMENTS ................................................................................................ x
ABSTRACT OF THE THESIS ......................................................................................... xi
1. Introduction ..................................................................................................................... 1
1.1 Plasmonics ................................................................................................................. 1
1.2 Top-down and Bottom-up Manufacturing ................................................................ 2
1.3 Nanoparticle Geometries ........................................................................................... 3
1.4 Chapter 1 References ................................................................................................ 4
2. Modeling the Optical Properties of Bowtie Antenna Generated By Self-Assembled Ag
Triangular Nanoprisms ....................................................................................................... 6
2.1 Introduction ............................................................................................................... 6
2.2 Methodology ............................................................................................................. 9
2.3 Results and Discussion ............................................................................................ 14
2.4 Conclusion ............................................................................................................... 27
2.5 Chapter 2 References .............................................................................................. 28
3. Nanocube Metasurfaces Displaying Extreme Light Confinement in the Infrared ....... 31
3.1 Introduction ............................................................................................................. 31
3.2 Methodology ........................................................................................................... 33
3.3 Results and Discussion ............................................................................................ 35
3.5 Appendix A ............................................................................................................. 38
3.6.1 lsfstart.lsf .......................................................................................................... 39
3.6.2 getparameters.m ................................................................................................ 42
3.6.3 nonauto.lsf ........................................................................................................ 46
3.6.4 nonauto.m ......................................................................................................... 47
3.4 Chapter 3 References .............................................................................................. 53
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4. Fluorophores as Gain Media and their Incorporation into the Nanocube Metasurfaces
........................................................................................................................................... 56
4.1 Introduction ............................................................................................................. 56
4.2 Methodology ........................................................................................................... 58
4.3 Results and Discussion ............................................................................................ 59
4.4 Future Directions ..................................................................................................... 61
4.5 Chapter 4 References .............................................................................................. 62

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LIST OF FIGURES
Figure 2.1. (a) UV-Vis extinction spectra of colloidal Ag nanoprisms. Inset shows a SEM
image of unassembled nanoprisms. (b) Simulated electric field enhancement (|E|/|E |)
o
spectra of a single Ag nanoprism. Inset shows the areas of high electric field present at the
resonance wavelength of =679 nm. .................................................................................. 7

Figure 2.2. (a) SEM image of self-assembled colloidal nanoprisms into bowtie structures.
(b,c) Simulated near-field intensities for the perfectly assembled bowtie structure taken in
the xy-plane (at z=0) under (b) x-polarization and (c) y-polarization. ............................. 15

Figure 2.3. (a) Simulated spectra of the changes in |E|/|E | as the gap distance of the bowtie
o
structure increases. (b) A plot of the calculated |E|/|E | at the mid-gap point versus the
o
bowtie gap distance. Also plotted for comparison is the calculated |E|/|E | for a single
o
triangular nanoprism at the equivalent distance away from the prism vertex.. ................ 16

Figure 2.4. (a) Color maps of the near-field intensities in the yz-plane as the thickness of
the nanoprisms comprising the assembled bowtie structure in increased. (b) The calculated
|E|/|E | ................................................................................................................................ 18
o

Figure 2.5. (a) Calculated spectra of |E|/|E | and (b) corresponding far-field scattering
o
efficiencies for the Ag nanoprism-based bowtie antennae as the radii of curvature of the
nanoprism vertexes are increased. (c) Confinement of the electric field in the xy-plane each
with increasing radius of curvature. .................................................................................. 20

Figure 2.6. (a) Schematic showing how rotation of misaligned bowtie structures is
determined by taking the angle  between the gap bisector and the nanoprism bisector. A
perfect bowtie structure corresponds to =90°. (b,c) Color maps of the near-field intensities
in the xy plane of bowtie structures corresponding to (b) the perfect bowtie dimer with
=90°, and (c) the misaligned structure with =30°. ........................................................ 22

Figure 2.7. Color maps of the calculated near-field intensities for misaligned bowtie
antenna. All images are taken as the cross-section of the bowtie structure with the xy-plane.
The color maps show the near-field intensities for (a) the higher-order resonance generated
by prism rotation. .............................................................................................................. 24

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Figure 2.8. (a) Calculated far-field scattering efficiency spectra for a nanoprism trimer
composed of three nanoprisms oriented into =90° bowtie junctions under illumination
with both x- and y-polarized light. (b) Color maps of the calculated near-field intensities
for the trimer at the strongest resonances, as indicated by the spectral peaks in (a). ....... 26

Figure 3.1 | FDTD simulations of NOM metasurfaces with varying interparticle spacing.
(a) Reflectance spectra of simulated NOM arrays of 92 nm Ag nanocubes with d=4-300
nm. (b) Plot showing exponential trend of fundamental resonance wavelength as a function
of interparticle spacing. ..................................................................................................... 35

Figure 4.1. a) Absorption and photoluminescence spectra of rhodamine 6G. b) Absorbtion
and photoluminescence of CdSe Quantum dots show their broad absorbance at
wavelengths below the initial absorption peak. ................................................................ 57

Figure 4.2. a) Optical microscope image of rhodamine 6G in PMMA that has been spun
coated and annealed onto a silicon substrate under 10x magnification. Inset of a) shows a
zoomed in (100x) image of one of the R6G crystals. B) Optical microscope image of
rhodamine 6G in PS. It can be observed that crystallization is also present. ................... 60

Figure 4.3. a) TEM image of CdSe QDs show there size of ~3.5 nm. Also visible is excess
organics. b) SEM image of a spun coat QD film showing aggregation of the QDs and
additional organic charging effects. c) Optical microscope image showing the QD
aggregates. d) Fluorescence microscope image indicating that the QDs are located in the
visible crystals. .................................................................................................................. 61

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LIST OF SCHEMES
Scheme 3.1. Flowchart for the Lumerical and MATLAB scripts used to generate 2D
electric and magnetic field images. The user first runs lsfstart.lsf and chooses the lumerical
file that the images are to be gotten from. The script then proceeds to open the graphical
user interface (GUI) and then generate images based on the selected options.....................38

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