76 research outputs found
Optical conductivity of metals from first principles
A computational method to obtain optical conductivities from first principles
is presented. It exploits a relation between the conductivity and the complex
dielectric function, which is constructed from the full electronic band
structure within the random-phase approximation. In contrast to the Drude
model, no empirical parameters are used. As interband transitions as well as
local-field effects are properly included, the calculated spectra are valid
over a wide frequency range. As an illustration I present quantitative results
for selected simple metals, noble metals, and ferromagnetic transition metals.
The implementation is based on the full-potential linearized
augmented-plane-wave method.Comment: 3 pages including 5 figure
All-dielectric one-dimensional periodic structures for total omnidirectional reflection and partial spontaneous emission control
A remarkable property of one-dimensional all-dielectric periodic structures
has recently been reported, namely a one-dimensional lattice can totally
reflect electromagnetic wave of any polarization at all angles within a
prescribed frequency region. Unlike their metallic counterpart, such
all-dielectric omnidirectional mirrors are nearly free of loss at optical
frequencies. Here we discuss the physics, design criteria and applications of
the thin-film all-dielectric omnidirectional mirror. The experimental
demonstration of the mirror is presented at optical frequencies.Comment: 6 pages, 9 figures; submitted to IEEE Journal of Lightwave Technolog
Observation of total omnidirectional reflection from a one-dimensional dielectric lattice
We show that under certain conditions one-dimensional dielectric lattice
possesses total omnidirectional reflection of incident light. The predictions
are verified experimentally using Na3AlF6/ZnSe multilayer structure developed
by means of standard optical technology. The structure was found to exhibit
reflection coefficient more then 99% in the range of incident angles 0-86
(degree) at the wavelength of 632.8 nm for s-polarization. The results are
believed to stimulate new experiments on photonic crystals and controlled
spontaneous emission.Comment: 4 pages, 5 figures; submitted to Applied Physics
Graphene hyperlens for terahertz radiation
We propose a graphene hyperlens for the terahertz (THz) range. We employ and
numerically examine a structured graphene-dielectric multilayered stack that is
an analogue of a metallic wire medium. As an example of the graphene hyperlens
in action we demonstrate an imaging of two point sources separated with
distance . An advantage of such a hyperlens as compared to a
metallic one is the tunability of its properties by changing the chemical
potential of graphene. We also propose a method to retrieve the hyperbolic
dispersion, check the effective medium approximation and retrieve the effective
permittivity tensor.Comment: 5 pages, 5 figure
Recommended from our members
Multiphysics simulations of adaptive metasurfaces at the meta-atom length scale
Adaptive metasurfaces (MSs) provide immense control over the phase, amplitude and propagation direction of electromagnetic waves. Adopting phase-change materials (PCMs) as an adaptive medium allows us to tune functionality of MSs at the meta-atom length scale providing full control over MS (re-)programmability. Recent experimental progress in the local switching of PCM-based MSs promises to revolutionize adaptive photonics. Novel possibilities open new challenges, one of which is a necessity to understand and be able to predict the phase transition behavior at the sub-micrometer scale. A meta-atom can be switched by a local deposition of heat using optical or electrical pulses. The deposited energy is strongly inhomogeneous and the resulting phase transition is spatially non-uniform. The drastic change of the material properties during the phase transition leads to time-dependent changes in the absorption rate and heat conduction near the meta-atom. These necessitate a self-consistent treatment of electromagnetic, thermal and phase transition processes. Here, a self-consistent multiphysics description of an optically induced phase transition in MSs is reported. The developed model is used to analyze local tuning of a perfect absorber. A detailed understanding of the phase transition at the meta-atom length scale will enable a purposeful design of programmable adaptive MSs. © 2020 Sebastian Meyer, Dmitry N. Chigrin et al., published by De Gruyter, Berlin/Boston 2020
Layer-Resolved Resonance Intensity of Evanescent Polariton Modes in Anisotropic Multilayers
Phonon polariton modes in layered anisotropic heterostructures are a key
building block for modern nanophotonic technologies. The light-matter
interaction for evanescent excitation of such a multilayer system can be
theoretically described by a transfer matrix formalism. This method allows to
compute the imaginary part of the p-polarized reflection coefficient
Im, which is typically used to analyze the polariton dispersion of
the multilayer structure, but lacks the possibility to access the
layer-resolved polaritonic response. We present an approach to compute the
layer-resolved polariton resonance intensity in aribtrarily anisotropic layered
heterostructures, based on calculating the Poynting vector extracted from a
transfer matrix formalism. Our approach is independent of the experimental
excitation conditions, and fulfills an empirical conservation law. As a test
ground, we study two state-of-the-art nanophotonic multilayer systems, covering
strong coupling and tunable hyperbolic surface phonon polaritons in twisted
\MoO~double layers. Providing a new level of insight into the polaritonic
response, our method holds great potential for understanding, optimizing and
predicting new forms of polariton heterostructures in the future.Comment: 7 pages, 2 figure
- …