Transformation Optics Applied to Plasmonics
Author(s)
Luo, Yu
Type
Thesis
Abstract
Lately, transformation optics (TO) has driven the development of metamaterial
science, providing a direct link between a desired electromagnetic phenomenon and
the material response required for its occurrence. However, this powerful framework
is not restricted to the metamaterial design, and it has recently been exploited to study
surface plasmon assisted phenomena. In this thesis, we mainly focus on the general
strategy based on TO to design and study analytically plasmonic devices capable of
efficiently harvesting light over a broadband spectrum and achieving considerable
field confinement and enhancement.
Using TO, we show that a finite nanoparticle with sharp geometrical features can
behave like an infinite plasmonic system, thereby allowing simultaneously a broadband
interaction with the incoming light as well as a spectacular nanofocusing of its
energy. Various plasmonic structures are designed and studied, such as 2D crescents,
groove/wedge like nanostructures, overlapping nanowires, and rough metal surfaces.
Comprehensive discussions are also provided on practical issues of this problem.
First, we discuss how the edge rounding at the sharp boundary affects the local field
enhancement as well as the energy and bandwidth of each plasmonic resonance. In
particular, the necessary conditions for achieving broadband light harvesting with
blunt structures are highlighted. The TO approach is then applied to study the
interaction between plasmonic nanoparticles. We demonstrate that the energy and
spectral shape of the localized surface plasmon resonances can be precisely controlled
by tuning the separation between the nanoparticles. Finally, we consider the extension
of the TO framework to 3D geometries, and show that the 3D structure is more robust
to radiative loss than its 2D counterpart.
The physical insights into sharp and blunt plasmonic nanostructures presented in
this thesis may be of great interest for the design of broadband light-harvesting
devices, invisible and non-invasive biosensors, and slowing-light devices.
science, providing a direct link between a desired electromagnetic phenomenon and
the material response required for its occurrence. However, this powerful framework
is not restricted to the metamaterial design, and it has recently been exploited to study
surface plasmon assisted phenomena. In this thesis, we mainly focus on the general
strategy based on TO to design and study analytically plasmonic devices capable of
efficiently harvesting light over a broadband spectrum and achieving considerable
field confinement and enhancement.
Using TO, we show that a finite nanoparticle with sharp geometrical features can
behave like an infinite plasmonic system, thereby allowing simultaneously a broadband
interaction with the incoming light as well as a spectacular nanofocusing of its
energy. Various plasmonic structures are designed and studied, such as 2D crescents,
groove/wedge like nanostructures, overlapping nanowires, and rough metal surfaces.
Comprehensive discussions are also provided on practical issues of this problem.
First, we discuss how the edge rounding at the sharp boundary affects the local field
enhancement as well as the energy and bandwidth of each plasmonic resonance. In
particular, the necessary conditions for achieving broadband light harvesting with
blunt structures are highlighted. The TO approach is then applied to study the
interaction between plasmonic nanoparticles. We demonstrate that the energy and
spectral shape of the localized surface plasmon resonances can be precisely controlled
by tuning the separation between the nanoparticles. Finally, we consider the extension
of the TO framework to 3D geometries, and show that the 3D structure is more robust
to radiative loss than its 2D counterpart.
The physical insights into sharp and blunt plasmonic nanostructures presented in
this thesis may be of great interest for the design of broadband light-harvesting
devices, invisible and non-invasive biosensors, and slowing-light devices.
Date Issued
2012-08
Date Awarded
2012-11
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Pendry, John
Sponsor
Lee Family Scholarship
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)