545 research outputs found
Theoretical investigation of one-dimensional cavities in two-dimensional photonic crystals
We study numerically the features of the resonant peak of one-dimensional
(1-D) dielectric cavities in a two-dimensional (2-D) hexagonal lattice. We use
both the transfer matrix method and the finite difference time-domain (FDTD)
method to calculate the transmission coefficient. We compare the two methods
and discuss their results for the transmission and quality factor Q of the
resonant peak. We also examine the dependence of Q on absorption and losses,
the thickness of the sample and the lateral width of the cavity. The Q- factor
dependence on the width of the source in the FDTD calculations is also given.Comment: 25 pages, 8 figure
Formation of robust and completely tunable resonant photonic band gaps
We identify different types of the photonic band gaps (PBGs) of two
dimensional magnetic photonic crystals (MPCs) consisting of arrays of magnetic
cylinders and study the different tunability (by an external static magnetic
field) of these PBGs. One type of the band gaps comes from infinitely
degenerate flat bands and is closely related to those in the study of
plasmonics. In addition, such PBGs are magnetically tunable and robust against
position disorder. We calcualte the transmission of the PBG's and found
excellent agreement with the results of the photonic band structure
calculation. Positional disorder of the lattice structure affects the different
types of PBGs differently.Comment: 4 pages, 5 figure
Numerical Investigation of Light Scattering off Split-Ring Resonators
Recently, split ring-resonators (SRR's) have been realized experimentally in
the near infrared (NIR) and optical regime. In this contribution we numerically
investigate light propagation through an array of metallic SRR's in the NIR and
optical regime and compare our results to experimental results.
We find numerical solutions to the time-harmonic Maxwell's equations by using
advanced finite-element-methods (FEM). The geometry of the problem is
discretized with unstructured tetrahedral meshes. Higher order, vectorial
elements (edge elements) are used as ansatz functions. Transparent boundary
conditions and periodic boundary conditions are implemented, which allow to
treat light scattering problems off periodic structures.
This simulation tool enables us to obtain transmission and reflection spectra
of plane waves which are incident onto the SRR array under arbitrary angles of
incidence, with arbitrary polarization, and with arbitrary
wavelength-dependencies of the permittivity tensor. We compare the computed
spectra to experimental results and investigate resonances of the system.Comment: 9 pages, 8 figures (see original publication for images with a better
resolution
Magnetic metamaterials at telecommunication and visible frequencies
Arrays of gold split-rings with 50-nm minimum feature size and with an LC
resonance at 200-THz frequency (1500-nm wavelength) are fabricated. For normal
incidence conditions, they exhibit a pronounced fundamental magnetic mode,
arising from a coupling via the electric component of the incident light. For
oblique incidence, a coupling via the magnetic component is demonstrated as
well. Moreover, we identify a novel higher-order magnetic resonance at around
370 THz (800-nm wavelength) that evolves out of the Mie resonance for oblique
incidence. Comparison with theory delivers good agreement and also shows that
the structures allow for a negative magnetic permeability.Comment: 4 pages, 3 figure
Refraction at Media with Negative Refractive Index
We show that an electromagnetic (EM) wave undergoes negative refraction at
the interface between a positive and negative refractive index material. Finite
difference time domain (FDTD) simulations are used to study the time evolution
of an EM wave as it hits the interface. The wave is trapped temporarily at the
interface and after a long time, the wave front moves eventually in the
negative direction. This explains why causality and speed of light are not
violated in spite of the negative refraction always present in a negative index
material.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Let
Trapping of Vibrational Energy in Crumpled Sheets
We investigate the propagation of transverse elastic waves in crumpled media.
We set up the wave equation for transverse waves on a generic curved, strained
surface via a Langrangian formalism and use this to study the scaling behaviour
of the dispersion curves near the ridges and on the flat facets. This analysis
suggests that ridges act as barriers to wave propagation and that modes in a
certain frequency regime could be trapped in the facets. A simulation study of
the wave propagation qualitatively supported our analysis and showed
interesting effects of the ridges on wave propagation.Comment: RevTex 12 pages, 7 figures, Submitted to PR
Twisted split-ring-resonator photonic metamaterial with huge optical activity
Coupled split-ring-resonator metamaterials have previously been shown to
exhibit large coupling effects, which are a prerequisite for obtaining large
effective optical activity. By a suitable lateral arrangement of these building
blocks, we completely eliminate linear birefringence and obtain pure optical
activity and connected circular optical dichroism. Experiments at around
100-THz frequency and corresponding modeling are in good agreement. Rotation
angles of about 30 degrees for 205nm sample thickness are derived.Comment: 6 pages, 4 figure
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