120 research outputs found
Gap and channelled plasmons in tapered grooves: a review
Tapered metallic grooves have been shown to support plasmons --
electromagnetically coupled oscillations of free electrons at metal-dielectric
interfaces -- across a variety of configurations and V-like profiles. Such
plasmons may be divided into two categories: gap-surface plasmons (GSPs) that
are confined laterally between the tapered groove sidewalls and propagate
either along the groove axis or normal to the planar surface, and channelled
plasmon polaritons (CPPs) that occupy the tapered groove profile and propagate
exclusively along the groove axis. Both GSPs and CPPs exhibit an assortment of
unique properties that are highly suited to a broad range of cutting-edge
nanoplasmonic technologies, including ultracompact photonic circuits,
quantum-optics components, enhanced lab-on-a-chip devices, efficient
light-absorbing surfaces and advanced optical filters, while additionally
affording a niche platform to explore the fundamental science of plasmon
excitations and their interactions. In this Review, we provide a research
status update of plasmons in tapered grooves, starting with a presentation of
the theory and important features of GSPs and CPPs, and follow with an overview
of the broad range of applications they enable or improve. We cover the
techniques that can fabricate tapered groove structures, in particular
highlighting wafer-scale production methods, and outline the various photon-
and electron-based approaches that can be used to launch and study GSPs and
CPPs. We conclude with a discussion of the challenges that remain for further
developing plasmonic tapered-groove devices, and consider the future directions
offered by this select yet potentially far-reaching topic area.Comment: 32 pages, 34 figure
Optical Microscopy of 3D Carpet Cloaks : Ray-Tracing Calculations
In a recent publication (T. Ergin et al., Science 328, 337 (2010)), three-dimensional broadband dielectric carpet cloaks have been fabricated and experimentally characterized by optical bright-field and dark-field microscopy using unpolarized light from an incandescent lamp. A direct comparison with theory has not been provided so far. In the present work, we treat the carpet cloak as well as the entire optical microscope within the ray-optics approximation and the cloak within the effective-medium approximation. We find good qualitative agreement between experimental results and our calculations
Introduction
Ce volume d’Études de lettres est la dernière d’une série de publications dédiées, en 2019, à Denis de Rougemont. Articulées autour d’une exposition et d’une série de conférences tenues au printemps à Neuchâtel, elles ont été menées avec le concours du projet Rougemont 2.0 développé à Genève, en vue de l’édition numérique des œuvres complètes de l’écrivain. Destinées à rappeler l’actualité de la pensée de Denis de Rougemont sur l’Europe et l’éducation, ces manifestations ont paru revêtir un c..
Blueshift of the surface plasmon resonance in silver nanoparticles: substrate effects
We study the blueshift of the surface plasmon (SP) resonance energy of
isolated Ag nanoparticles with decreasing particle diameter, which we recently
measured using electron energy loss spectroscopy (EELS). As the particle
diameter decreases from 26 down to 3.5 nm, a large blueshift of 0.5 eV of the
SP resonance energy is observed. In this paper, we base our theoretical
interpretation of our experimental findings on the nonlocal hydrodynamic model,
and compare the effect of the substrate on the SP resonance energy to the
approach of an effective homogeneous background permittivity. We derive the
nonlocal polarizability of a small metal sphere embedded in a homogeneous
dielectric environment, leading to the nonlocal generalization of the classical
Clausius-Mossotti factor. We also present an exact formalism based on multipole
expansions and scattering matrices to determine the optical response of a metal
sphere on a dielectric substrate of finite thickness, taking into account
retardation and nonlocal effects. We find that the substrate-based calculations
show a similar-sized blueshift as calculations based on a sphere in a
homogeneous environment, and that they both agree qualitatively with the EELS
measurements.Comment: Invited paper for SPP6 special issue to be published in Opt. Expres
On the feasibility of pentamode mechanical metamaterials
Conceptually, all conceivable three-dimensional mechanical materials can be
built from pentamode materials. Pentamodes also enable to implement
three-dimensional transformation acoustics - the analogue of transformation
optics. However, pentamodes have not been realized experimentally to the best
of our knowledge. Here, we investigate inasmuch the pentamode theoretical ideal
suggested by Milton and Cherkaev in 1995 can be approximated by a metamaterial
with current state-of-the-art lithography. Using numerical calculations
calibrated by our fabricated three-dimensional microstructures, we find that
the figure of merit, i.e., the ratio of bulk modulus to shear modulus, can
realistically be made as large as about 1,000.Comment: 4 pages and 5 figure
Optical reconfiguration and polarization control in semi-continuous gold films close to the percolation threshold
Controlling and confining light by exciting plasmons in resonant metallic
nanostructures is an essential aspect of many new emerging optical
technologies. Here we explore the possibility of controllably reconfiguring the
intrinsic optical properties of semi-continuous gold films, by inducing
permanent morphological changes with a femtosecond (fs)-pulsed laser above a
critical power. Optical transmission spectroscopy measurements show a
correlation between the spectra of the morphologically modified films and the
wavelength, polarization, and the intensity of the laser used for alteration.
In order to understand the modifications induced by the laser writing, we
explore the near-field properties of these films with electron energy-loss
spectroscopy (EELS). A comparison between our experimental data and full-wave
simulations on the exact film morphologies hints toward a restructuring of the
intrinsic plasmonic eigenmodes of the metallic film by photothermal effects. We
explain these optical changes with a simple model and demonstrate
experimentally that laser writing can be used to controllably modify the
optical properties of these semi-continuous films. These metal films offer an
easy-to-fabricate and scalable platform for technological applications such as
molecular sensing and ultra-dense data storage.Comment: Supplementary materials available upon request ([email protected]
Signatures of Non-Markovianity in Cavity-QED with Color Centers in 2D Materials
Light-matter interactions of defects in two dimensional materials are
expected to be profoundly impacted by strong coupling to phonons. In this work,
we combine ab initio calculations of a defect in hBN, with a fully quantum
mechanical and numerically exact description of a cavity-defect system to
elucidate this impact. We show that even at weak light-matter coupling, the
dynamical evolution of the cavity-defect system has clear signatures of
non-markovian phonon effects, and that linear absorption spectra show the
emergence of hybridised light-matter-phonon states in regimes of strong
light-matter coupling. We emphasise that our methodology is general, and can be
applied to a wide variety of material/defect systems.Comment: 7 pages, 3 figures + 8 pages supplemen
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Importance of substrates for the visibility of "dark" plasmonic modes
Dark plasmonic modes have interesting properties, including longer lifetimes and narrower linewidths than their radiative counterpart, and little to no radiative losses. However, they have not been extensively studied yet due to their optical inaccessibility. In this work, we systematically investigated the dark radial breathing modes (RBMs) in monocrystalline gold nanodisks, specifically their outcoupling behavior into the far-field by cathodoluminescence spectroscopy. Increasing the substrate thickness resulted in an up to 4-fold enhanced visibility. This is attributed to breaking the mirror symmetry by the high-index substrate, creating an effective dipole moment. Furthermore, the resonance energy of the dark RMBs can be easily tuned by varying the nanodisk diameter, making them promising candidates for nanophotonic applications. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen
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