We report on the optical properties of a layer-by-layer structure of silver nanorods, with their axes aligned
perpendicular to the z direction and mutually twisted through an angle of 60° from layer to layer, by means
of rigorous full electrodynamic calculations using the layer-multiple-scattering method, properly extended to
describe axis-symmetric particles with arbitrary orientation. We analyze the complex photonic band structure of
this crystal in conjunction with relevant polarization-resolved transmission spectra of finite slabs of it and explain
the nature of the different eigenmodes of the electromagnetic field in the light of group theory. Our results reveal
the existence of sizable polarization gaps and demonstrate the occurrence of strong optical activity and circular
dichroism, combined with reduced dissipative losses, which make the proposed architecture potentially useful for
practical applications as ultrathin circular polarizers and polarization rotators.
Light control through elastic waves is a well established and mature technology. The underlying mechanism is
the scattering of light due to the dynamic modulation of the refractive index and the material interfaces caused
by an elastic wave, the so-called acousto-optic interaction. This interaction can be enhanced in appropriately
designed structures that simultaneously localize light and elastic waves in the same region of space and operate
as dual optical-elastic cavities, often called phoxonic or optomechanical cavities. Typical examples of phoxonic
cavities are multilayer films with a dielectric sandwiched between two Bragg mirrors or, in general, defects in
macroscopically periodic structures that exhibit dual band gaps for light and elastic waves. In the present work
we consider dielectric particles as phoxonic cavities and study the influence of elastic eigenmode vibrations on the
optical Mie resonances. An important issue is the excitation of elastic waves in such submicron particles and, in
this respect, we analyze the excitation of high-frequency vibrations following thermal expansion induced by the
absorption of a femtosecond laser pulse. For spherical particles, homogeneous thermalization leads to excitation
of the particle breathing modes. We report a thorough study of the acousto-optic interaction, correct to all
orders in the acousto-optic coupling parameter, by means of rigorous full electrodynamic and elastodynamic
calculations, in both time and frequency domains. Our results show that, under double elastic-optical resonance
conditions, strong acousto-optic interaction takes place and results in large dynamical shifts of the high-Q optical
Mie resonances, manifested through multiphonon exchange mechanisms.
Periodic media offer impressive opportunities to manipulate the transport of classical waves namely light or sound.
Elastic waves can scatter light through the so-called acousto-optic interaction which is widely used to control
light in telecommunication systems and, additionally, the radiation pressure of light can generate elastic waves.
Concurrent control of both light and sound through simultaneous photonic-phononic, often called phoxonic, bandgap
structures is intended to advance both our understanding as well as our ability to manipulate light with
sound and vise versa. In particular co-localization of light and sound in phoxonic cavities could trigger nonlinear
absorption and emission processes and lead to enhanced acousto-optic effects. In the present communication,
we present our efforts towards the design of different phoxonic crystal architectures such as three-dimensional
metallodielectric structures, two-dimensional patterned silicon slabs and simple one-dimensional multilayers,
and provide optimum parameters for operation at telecom light and GHz sound. These structures can be used
to design phoxonic cavities and study the acousto-optic interaction of localized light and sound, or phoxonic
waveguides for tailored slow light-slow sound transport. We also discuss the acousto-optic interaction in onedimensional
multilayer structures and study the enhanced modulation of light by acoustic waves in a phoxonic
cavity, where a consistent interpretation of the physics of the interaction can be deduced from the time evolution
of the scattered optical field, under the influence of an acoustic wave.
We present a thorough theoretical study of the optical properties of periodic structures built of silver and silica
nanodisks in a sandwich-like configuration, by means of full electrodynamic calculations using the extended
layer-multiple-scattering method. The strong coupling of the metallic nanoparticles and the resulting plasmon
hybridization lead to collective electric and magnetic resonant modes, which can be tuned by changing the
structural parameters, such as nanoparticle size and lattice constant. We analyze the response of single- and
multi-layer architectures of ordered arrays of such nanosandwiches on a dielectric substrate to externally incident
light and evaluate the corresponding effective permittivity and permeability functions. Our results reveal the
existence of optical magnetism, with a strong negative effective permeability over a tunable spectral range at
near-infrared and visible frequencies. We introduce the complex photonic band structure as a tool in the study
of three-dimensional metamaterials and establish additional criteria for the validity of their effective-medium
description. Our work demonstrates the efficiency of the recently developed extended layer-multiple-scattering
method in the study of metamaterials of composite metal-dielectric particles of arbitrary shape.
Periodic nanostructures for plasmonic engineering, comprising one or two types of silica core - metallic shell spherical particles, are studied by means of full electrodynamic calculations using the layer-multiple-scattering method. The complex photonic band structure of such three-dimensional crystals is analyzed in conjunction with relevant transmission spectra of corresponding finite slabs and the physical origin of the different optical modes is elucidated, providing a consistent interpretation of the underlying physics. In the case of binary structures, collective plasmonic modes originating from the two building components coexist, leading to broadband absorption and a rich structure of resonances and hybridization gaps over an extended frequency range.
We present an efficient computational methodology for full electrodynamic calculations of metallodielectric nanostructures
based on a multiple-scattering formulation of Maxwell's equations. The method, originally developed
for systems of spherical particles (MULTEM code), is extended to systems of particles of arbitrary shape and
applied to ordered structures of metallic nanodisks with an aspect ratio as large as five. We first discuss the particle
plasmon resonances of single metallic nanocylinders of different aspect ratios. Then, we study the plasmonic
excitations of square arrays of metal-dielectric-metal nanosandwiches and the optical response of a rectangular
lattice of metallic nanodisks on a dielectric waveguide. Finally we analyse the photonic band structure of a
simple cubic crystal of metallic nanodisks.