Metamaterial Super Absorber for Light

110 Pages·2017·3.07 MB·English

Metamaterial Super Absorber for Light-
Matter Interaction: from Broadband to
Extreme Field Confinement
by
Dengxin Ji
February, 2018
A Dissertation Submitted to the
Faculty of the Graduate School of
the University at Buffalo, State University of New York
in Partial Fulfillment of the Requirement for the
Degree of
Doctor of Philosophy
Department of Electrical Engineering
This dissertation is approved and recommended for acceptance as a
dissertation in partial fulfillment of the requirements for the degree of
Doctor of Philosophy in Electrical Engineering.
____________________
Data
____________________
Accepted Date
Committee Members:
____________________ ____________________
Dr. Qiaoqiang Gan (Dissertation Director) Date
____________________ ____________________
Dr. Edward Furlani Date
____________________ ____________________
Dr. Pao-Lo Liu Date
____________________ ____________________
Dr. Hao Zeng Date
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Acknowledgements
First and foremost, I would like to express my sincere gratitude to my advisor Prof.
Qiaoqiang Gan for his support, encouragement, and inspiration in the last six years of my
Ph.D. study. All the achievements presented in this doctoral dissertation would not have
been possible without the support and contribution from him. His scientific vision, critical
thinking, and creativity are remarkable. Under his guidance, I feel that I matured
significantly, especially in setting short-term and long-term research targets, and
conceiving and establishing research plans. I feel truly lucky to be Prof. Gan’s student and
have benefited in every possible way that a student can benefit under his extreme support
and guidance. In addition to his role as my advisor, I have also enjoyed his friendship over
the years.
I am also grateful to Prof. Edward Furlani, Prof. Pao-Lo Liu, and Prof. Hao Zeng as
my committee members for their help to complete this dissertation.
I would like to thank Prof. Haifeng Hu (from Northeastern University, China), for his
advices and collaboration in my Ph.D. study. The presented hyperbolic metamaterial super
absorber is a beautiful cutting-edge project that requires strong theoretical physics and
nanophotonic background. I cannot image I can accomplish this much if not with his
expertise and advices throughout these years. I will thank Prof. Alexander N. Cartwright,
Prof. Zongfu Yu (from University of Wisconsin-Madison), and Prof. Suhua Jiang (from
Fundan University), for their expertise and valued advice.
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Working in the Nano-optics & Biophotonics lab has been a great experience for me in
my Ph.D. studies. I appreciate the assistance from my group mates, Dr. Xie Zeng, Dr.
Haomin Song, Mr. Nan Zhang, Mrs. Youhai Liu, Mr. Lyu Zhou, Mr. Matthew Singer, Mr.
Chenyu Li, Mr. Qingyang Liu, Mr. Chu Wang, Dr. Zhejun Liu, and Ms. Yanbo Guo. I also
appreciate my friends in University at Buffalo, including Jingbo Sun, Borui Chen, Alec
Cheney, Yuan Yuan, Feng Zhang, Yunchen Yang, Chang Liu, etc.
I want to thank Nana Lin for your support.
Finally, I want to thank my parents, Yongqiang Ji and Yuqin Wang, for all the love
they gave me. It is because of your endless support, love, and caring that I can turn my
dream into reality. I want to dedicate this dissertation to my parents.
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T C
ABLE OF ONTENTS
Acknowledgements iii
List of Tables viii
List of Figures ix
Abstract xvi
1 Introduction 1
1.1 Background and Motivation 1
1.2 Metamaterial Super Absorber 2
1.2.1 Development of Metamaterial Super Absorber 2
1.2.2 Broadband MDM Super Absorber 4
1.2.3 Biosensing based on Metamaterial Super Absorber 6
1.3 Organization of This Thesis 7
1.4 References 10
2 Broadband Absorption Engineering of Hyperbolic Metamaterial (HMM) Patterns
14
2.1 Introduction 14
2.2 Light Trapping in Lossless and Lossy HMM Waveguide Tapers 15
2.2.1 Effective Medium Theory Model 16
2.2.2 Numerical Validation Using Real Optical Constants 24
2.2.3 Period Dependence 27
v
2.3 Multi-layered HMM Waveguide Taper Array for Broadband Absorption
Engineering 30
2.3.1 Experimental Realization of Multi-layered HMM Waveguide Taper Array
for Broadband Absorption 30
2.3.2 Multi-unit Pattern Array Based on Less Metal/Dielectric Films 36
2.3.3 Scattering Property of HMM Waveguide Taper Array 39
2.4 Summary 40
2.5 References 42
3 Surface Enhanced Infrared Absorption Spectroscopy Using Nanogap MDM Super
Absorber 48
3.1 Introduction 48
3.2 Interaction between adjacent patterns in planar MDM structures 50
3.2.1 Theoretical analysis of planar MDM structure 51
3.2.2 Spectral tunability in Terahertz (THz) domain 55
3.3 Efficient light trapping in corrugated MDM structure with ALD-defined gaps 56
3.3.1 Theoretical analysis of corrugated MDM structure 56
3.3.2 Experimental realization of corrugated MDM structure 58
3.4 Spectral tunability with fixed lateral dimensions 60
3.5 Summary 62
vi
3.6 References 64
4 Surface enhanced infrared absorption spectroscopy using nanogap MDM super
absorber 68
4.1 Surface enhanced sensing around ultra-small gaps 68
4.2 SEIRA for PMMA 69
4.2.1 Experimental results for PMMA molecules sensing 69
4.2.2 Enhancement factor calculation for PMMA coatings 71
4.2.3 Comparison of sensing area 74
4.3 SEIRA for ODT 75
4.3.1 Experimental results for ODT monolayer sensing 75
4.3.2 Enhancement factor calculation for ODT monolayer 76
4.4 Increasing the area occupied by nanogaps 81
4.5 Summary 82
4.6 References 83
5. Conclusions 86
Publications 88
VITA 91

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List of Tables
Table 2.1 Conditions for existence of TM , TM and TM modes in the HMM waveguide.
0 1 2
Consider that V kw /I I 11/2, the corresponding thickness of the HMM core layer
2  2z 1 2x 
to support |f> and |b> modes can therefore be determined.

viii
List of Figures

Fig. 1.1 Schematic illustrations of a) atoms in a natural material; b) artificially designed
“atoms” in a metamaterial. Figure reproduced from ref. [9].
Fig. 1.2 Simulated (red) and measured (blued) absorbance curve. The dashed gray
absorbance curve is a Gaussian weighted average of the metamaterials absorber. Inset:
schematic illustration of metamaterial super absorber proposed by Landy et al. Figure
reproduced from Ref. [10].
Fig. 1.3 Schematic diagrams of broadband metamaterial super absorber with a) parallel
distributed multi resonators (reproduced from ref. [23]), b) concentric square ring
resonators (reproduced from ref. [24]), and c) stacked multiple resonators (reproduced
from ref. [25]).
Fig. 1.4 Raman signal comparison of BPE molecules on the universal substrate (pink
curves), reference nanoparticles on glass (green curves) and two commercial products of
rSERS (blue curves) and QSERS (red curves) excited by five laser lines. Reproduced form
ref. [15].
Fig. 2.1 Propagation constants of TM0, TM1 and TM2 modes, β, as a function of the HMM
waveguide width. The two branches for each mode are separated by a degeneracy point,
represented by empty circles.
Fig. 2.2 Normalized power flows of TM , TM and TM modes, P , as a function of the
0 1 2 norm
HMM waveguide width.
Fig. 2.3 |E|-field distribution of TM , TM and TM modes in HMM waveguide tapers. In
0 1 2
the length of 3λ along the z-direction, the tapered width increases from 0.1λ to 0.22λ in the
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upper panel, from 0.3λ to 0.42λ in the middle panel, and from 0.55λ to 0.62λ in the lower
panel, respectively.
Fig. 2.4 The width-dependence of (a) the real part of the propagation constant, β , (b) the
r
attenuation coefficient, β.
i
Fig. 2.5 The effective modal area of the fundamental mode (TM ) in the lossy HMM
0
waveguide taper.
Fig. 2.6 The |E|-filed distribution in the HMM waveguide taper for the TM mode.
0
Fig. 2.7 a) The local modal amplitudes of | f+>, | f->, |b+> and |b-> modes along the z-
direction. b) The |E| -filed distribution for the | f+> mode (the upper half panel) and | b+>
mode (the lower half panel), respectively.
Fig. 2.8 Conceptual illustration of HMM waveguide taper arrays constructed by alternating
metal-dielectric films.
Fig. 2.9 The width-dependent dispersion curve for the propagation constants of λ=3.5 μm
(i.e. the real part, β , and the imaginary part, β).
r i
Fig. 2.10 |E|-field distributions in the (a) lossless and (b) lossy HMM waveguide tapers for
the TM modes, respectively.
0
Fig. 2.11 (a) 1D absorption cross-section of a single 8-pair HMM waveguide taper unit. (b)
Absorption spectra of three periodic patterns with the period of (A) 2.26 μm, (B) 1.35 μm
and (C) 1.14 μm.
Fig. 2.12 Modeled E-field distributions in (a) structure C and (b) structure A at the
wavelength of 5.15 μm.
Fig. 2.13 Modeled |E|-field distributions in the 8-paired HMM waveguide taper (i.e. sample
3).
x