Chapter 2 Nanofilm based perfect absorber - Rice Scholarship Home

167 Pages·2013·2.71 MB·English

ABSTRACT
Plasmonic properties and applications of metallic nanostructures
by
Yurong Zhen
Plasmonic properties and the related novel applications are studied on various
types of metallic nano-structures in one, two, or three dimensions. For 1D nanostruc-
ture,themotionoffreeelectronsinametal-filmwithnanoscalethicknessisconfinedin
its normal dimension and free in the other two. Describing the free-electron motion at
metal-dielectric surfaces, surface plasmon polariton (SPP) is an elementary excitation
of such motions and is well known. When further perforated with periodic array of
holes, periodicity will introduce degeneracy, incur energy-level splitting, and facilitate
the coupling between free-space photon and SPP. We applied this concept to achieve
a plasmonic perfect absorber. The experimentally observed reflection dip splitting
is qualitatively explained by a perturbation theory based on the above concept. If
confined in 2D, the nanostructures become nanowires that intrigue a broad range of
research interests. We performed various studies on the resonance and propagation
of metal nanowires with different materials, cross-sectional shapes and form factors,
in passive or active medium, in support of corresponding experimental works. Finite-
Difference Time-Domain (FDTD) simulations show that simulated results agrees well
with experiments and makes fundamental mode analysis possible. Confined in 3D,
the electron motions in a single metal nanoparticle (NP) leads to localized surface
plasmon resonance (LSPR) that enables another novel and important application:
plasmon-heating. By exciting the LSPR of a gold particle embedded in liquid, the
excited plasmon will decay into heat in the particle and will heat up the surrounding
liquid eventually. With sufficient exciting optical intensity, the heat transfer from NP
to liquid will undergo an explosive process and make a vapor envelop: nanobubble.
We characterized the size, pressure and temperature of the nanobubble by a sim-
ple model relying on Mie calculations and continuous medium assumption. A novel
effective medium method is also developed to replace the role of Mie calculations.
The characterized temperature is in excellent agreement with that by Raman scat-
tering. If fabricated in an ordered cluster, NPs exhibit double-resonance features and
the double Fano-resonant structure is demonstrated to most enhance the four-wave
mixing efficiency.
Acknowledgments
First and foremost, thanks to my wife, Ting Li. You are the most important person
in the world to me. Without the help from you to take care of the family, I would
not have been able to focus on my PhD studies and meet the requirement within four
years.
Thanks to my parents and parents-in-law, you have been sacrificing your time and
energy a lot in helping my family.
I would like to acknowledge Professor Peter Nordlander for his great support and
the role as my advisor, as well as the chair of my committee. His has given me a
lot of freedom in research and his support and patience throughout this period have
been invaluable.
I would also like to acknowledge Professor Naomi Halas and Professor Jason
Hafner, not only for the co-authorship and the role as committee members, but also
for their insightful advice during my studies, and the unparalleled research opportu-
nities provided in tight theory-experiment collaboration.
Thisdissertation would nothavebeen possiblewithoutthehard workand support
of my other co-authors, as well as the funding agencies. Thank you all.
Parts of this dissertation are based on papers co-authored with my collaborators:
• Chapter2isbasedon”Tunablewide-angleplasmonicperfectabsorberatvisible
frequencies”, by Zheyu Fang, Yu-Rong Zhen, Linran Fan, Xing Zhu, and Peter
Nordlander, as it appears in [1].
• Section 3.1 is based on ”A Tunable Plasmon Resonance in Gold Nanobelts”, by
Lindsey J. E. Anderson,Courtney M. Payne, Yu-Rong Zhen,Peter Nordlander,
and Jason H. Hafner, as it appears in [2].
v
• Section 3.2 is being prepared for submission for publication by Lindsey J. E.
Anderson, Yu-Rong Zhen, Courtney M. Payne, Peter Nordlander, and Jason H.
Hafner.
• Section 3.3 is being prepared for submission for publication by Aniruddha
Paul,Yu-Rong Zhen, Yi Wang, Younan Xia, Peter Nordlander, and Stephan
Link.
• Section 4.1 has been accepted by Nano Letters for publication [3], and was
preparedbyZheyuFang,Yu-RongZhen, OaraNeumann, AlbertPolman,Javier
Garca de Abajo, Peter Nordlander, and Naomi J. Halas.
• Section 4.2 is being prepared for submission for publication by Yu-Rong Zhen,
Zheyu Fang, Javier Garca de Abajo, Naomi Halas and Peter Nordlander.
• Chapter 5 has been submitted to Proc. Nat. Acad. Sci. for review, and was
prepared by Yu Zhang, Fangfang Wen, Yu-Rong Zhen, Peter Nordlander, and
Naomi J. Halas
Special thanks to my group members and former group members, including but
not limited to, Kui Bao, Yang Li, Ke Zhao, Nicolas Large, Jorge Zuloaga, Heidar
Sobhani, Vikram Kulkarni, Yumin Wang, Tamer Ali, Feng Hao, Fei Le, Yanpeng
Wu, Lifei Liu, Yang Cao, Chizuko Dutta, Manvir Singh, etc.
Special thanks to the members in Halas group, Hafner group and Link group who
have shared ideas and exchanged opinions together.
Special thanks to my friends both inside and outside Rice, who gave me their
unwavering support (and, in some cases, the use of their couch).
Lastly, special thanks to my children, Xinyi Zhen and Lijia Zhen. I am profoundly
blessed to have all of you in my life.
Contents
Abstract ii
Acknowledgments iv
List of Figures ix
1 Introduction 1
1.1 Planar nanostructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Nanowire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Nanoparticle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1 Single nanoparticle and nanobubble . . . . . . . . . . . . . . . 7
1.3.2 Nanocluster . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2 Nanofilm based perfect absorber 15
2.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Experimental measurements . . . . . . . . . . . . . . . . . . . . . . . 17
2.3 Theoretical description . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3.1 Coupling mechanism . . . . . . . . . . . . . . . . . . . . . . . 20
2.3.2 A perturbative approach . . . . . . . . . . . . . . . . . . . . . 21
2.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3 Plasmonic properties of nanowires 31
3.1 Surface plasmon resonance of nanobelt . . . . . . . . . . . . . . . . . 31
3.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.1.2 Sharp resonance . . . . . . . . . . . . . . . . . . . . . . . . . . 33
vii
3.1.3 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.1.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.1.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.2 Propagation and electromagnetic confinement in nanobelt . . . . . . . 40
3.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.2.2 Propagation length measurements . . . . . . . . . . . . . . . . 43
3.2.3 Simulated properties of propagating modes . . . . . . . . . . . 47
3.2.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3 Stimulated emission of SPP in nanowire: dye-assisted propagation
length enhancement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3.2 Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.3.3 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.3.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4 Plasmon-heated bubble generation 64
4.1 Experimental characterization . . . . . . . . . . . . . . . . . . . . . . 64
4.1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.1.2 Experimental evidences of formed nanobubble . . . . . . . . . 67
4.1.3 Theoretical analysis . . . . . . . . . . . . . . . . . . . . . . . . 73
4.1.4 From nanobubble to microbubble . . . . . . . . . . . . . . . . 77
4.2 Local field weighted effective medium method . . . . . . . . . . . . . 81
4.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.2.2 Results and discussion . . . . . . . . . . . . . . . . . . . . . . 83
4.2.3 Benchmark test . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4.2.4 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.3 Determination of bubble pressure and temperature . . . . . . . . . . 96
4.4 Analysis of nanosphere surface temperature . . . . . . . . . . . . . . 97
viii
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5 Four-wave mixing in nanocluster 101
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.2 Double Fano-resonance structure . . . . . . . . . . . . . . . . . . . . 104
5.3 FWM measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.4 FDTD-assisted modelling . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.5 Control experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6 Conclusions 113
Bibliography 117
List of Figures
2.1 Schematic of the experimental configuration of the perfect absorber . 18
2.2 Experimental reflectance for varied hole radius . . . . . . . . . . . . . 19
2.3 Coupling mechanism from incident photons into the SPP and the
SPP’s lateral profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.4 Dispersion relation diagram of the hybridized surface plasmon
polariton in the unperturbed heterostructure . . . . . . . . . . . . . . 23
2.5 Three unperturbed eigenstates and the radius-dependent peak splitting 28
3.1 Dark field micrographs and corresponding single nanobelt spectra . . 33
3.2 Gold nanobelt simulation geometry, spectra and charge distributions
for TE illumination . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.3 Calculated charge distribution of the zig-zag mode by TM illumination. 37
3.4 The dependence of the plasmon resonance peak on cross-sectional
aspect ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.5 Gold nanobelts deposited on a substrate and imaged by dark-field
optical microscopy and by scanning electron microscopy . . . . . . . 44
3.6 Two gold nanobelts imaged with epi-bright field illumination and
focused illumination to display propagation . . . . . . . . . . . . . . . 45
3.7 Measured plasmon propagation lengths of gold nanobelts and silver
nanowires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.8 Dark-field image and simulated properties of propagating modes . . . 49
x
3.9 Experimentally verified cross-over of the propagating mode intensities
with parallel and perpendicular polarization . . . . . . . . . . . . . . 50
3.10 Cross-sections of normalized field and heat intensity in a 125 × 40
nm gold nanobelt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.11 Schematic description of the gain experiment . . . . . . . . . . . . . . 58
3.12 A representative gain experiment . . . . . . . . . . . . . . . . . . . . 59
3.13 FDTD simulation of SPP gain for a silver NW lying on top of a
dielectric/gain layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.1 Light-induced generation of a nanobubble at a single nanoparticle
surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.2 Temperature at the Au nanoparticle surface during the steam
generation process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.3 Nanobubble theoretical modeling . . . . . . . . . . . . . . . . . . . . 75
4.4 Coalescence of nanobubbles into micron-sized bubbles . . . . . . . . . 78
4.5 Experimental optical spectra for a gold nanosphere (NS) and the
effect of water temperature . . . . . . . . . . . . . . . . . . . . . . . . 85
4.6 Schematics and simulated scattered electric field intensity (|Esc|2) of
a plasmon-heated nanobubble around a gold nanosphere and its
ambience. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.7 Calculated bubble radius as a function of peak shift ratio with
different methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.1 FWM configuration and characterization of the double Fano resonant
plasmonic nanocluster . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.2 FWM Experiments by individual nanoclusters . . . . . . . . . . . . . 106
5.3 FDTD calculated near-field maps of the nanocluster . . . . . . . . . . 109
5.4 FWM control experiments . . . . . . . . . . . . . . . . . . . . . . . . 112