308 research outputs found
Transmission properties of composite metamaterials in free space
Cataloged from PDF version of article.We propose and demonstrate a type of composite metamaterial which is constructed by combining thin copper wires and split ring resonators (SRRs) on the same board. The transmission measurements performed in free space exhibit a passband within the stop bands of SRRs and thin wire structures. The experimental results are in good agreement with the predictions of the transfer matrix method simulations. (C) 2002 American Institute of Physics
Coupled optical microcavities in one-dimensional photonic bandgap structures
We present a detailed theoretical and experimental study of the evanescent coupled optical microcavity modes in one-dimensional photonic bandgap structures. The coupled-cavity samples are fabricated by depositing alternating hydrogenated amorphous silicon nitride and silicon oxide layers. Splitting of the eigenmodes and formation of a defect band due to interaction between the neighbouring localized cavity modes are experimentally observed. Corresponding field patterns and the transmission spectra are obtained by using transfer matrix method (TMM) simulations. A theoretical model based on the classical wave analogue of the tight-binding (TB) picture is developed and applied to these structures. Experimental results are in good agreement with the predictions of the TB approximation and the TMM simulations
Anisotropy and oblique total transmission at a planar negative-index interface
We show that a class of negative index (n) materials has interesting
anisotropic optical properties, manifest in the effective refraction index that
can be positive, negative, or purely imaginary under different incidence
conditions. With dispersion taken into account, reflection at a planar
negative-index interface exhibits frequency selective total oblique
transmission that is distinct from the Brewster effect.
Finite-difference-time-domain simulation of realistic negative-n structures
confirms the analytic results based on effective indices.Comment: to appear in Phys. Rev.
Transmission Losses in Left-handed Materials
We numerically analyze the origin of the transmission losses in left-handed
structures. Our data confirms that left handed structures can have very good
transmission properties, in spite of the expectable dispersion of their
effective permeability and refraction index. The large permittivity of the
metallic components improves the transmission. High losses, observed in recent
experiments, could be explained by the absorption of the dielectric board
Continuous Triboelectric Power Harvesting and Biochemical Sensing Inside Poly(vinylidene fluoride) Hollow Fibers Using Microfluidic Droplet Generation
[No abstract available
Isotropic photonic band gap and anisotropic structures in transmission spectra of two-dimensional 5-fold and 8-fold symmetric quasiperiodic photonic crystals
We measured and calculated transmission spectra of two-dimensional
quasiperiodic photonic crystals (PCs) based on a 5-fold (Penrose) or 8-fold
(octagonal) symmetric quasiperiodic pattern. The photonic crystal consisted of
dielectric cylindrical rods in air placed normal to the basal plane on vertices
of tiles composing the quasiperiodic pattern. An isotropic photonic band gap
(PBG) appeared in the TM mode, where electric fields were parallel to the rods,
even when the real part of a dielectric constant of the rod was as small as
2.4. An isotropic PBG-like dip was seen in tiny Penrose and octagonal PCs with
only 6 and 9 rods, respectively. These results indicate that local multiple
light scattering within the tiny PC plays an important role in the PBG
formation. Besides the isotropic PBG, we found dips depending on the incident
angle of the light. This is the first report of anisotropic structures clearly
observed in transmission spectra of quasiperiodic PCs. Based on rod-number and
rod-arrangement dependence, it is thought that the shapes and positions of the
anisotropic dips are determined by global multiple light scattering covering
the whole system. In contrast to the isotropic PBG due to local light
scattering, we could not find any PBGs due to global light scattering even
though we studied transmission spectra of a huge Penrose PC with 466 rods.Comment: One tex file for manuscript and 12 PNG files for figures consisting
of Fig.1a-d, 2,3, ...
Bose-Einstein condensation in a two-dimensional, trapped,interacting gas
We study Bose-Einstein condensation phenomenon in a two-dimensional (2D)
system of bosons subjected to an harmonic oscillator type confining potential.
The interaction among the 2D bosons is described by a delta-function in
configuration space. Solving the Gross-Pitaevskii equation within the two-fluid
model we calculate the condensate fraction, ground state energy, and specific
heat of the system. Our results indicate that interacting bosons have similar
behavior to those of an ideal system for weak interactions.Comment: LaTeX, 4 pages, 4 figures, uses grafik.sty (included), to be
published in Phys. Rev. A, tentatively scheduled for 1 October 1998 (Volume
58, Number 4
Are waves all localized in two dimensional random media?
It has been the dominant view for over two decades that all waves are
localized in two dimensions for any given amount of disorder. Here, I would
like to raise questions about this assertion. The discussion leads to the
conclusion that there is a lack of the conclusive and definite support of the
claim. Rather, the recent evidence tends to indicate that waves are not
necessarily always localized in two dimensional random systems. Reasons are
elaborated
Resonant and anti-resonant frequency dependence of the effective parameters of metamaterials
We present a numerical study of the electromagnetic response of the
metamaterial elements that are usedto construct materials with negative
refractive index. For an array of split ring resonators (SRR) we find that the
resonant behavior of the effective magnetic permeability is accompanied by an
anti-resonant behavior of the effective permittivity. In addition, the
imaginary parts of the effective permittivity and permeability are opposite in
sign. We also observe an identical resonant versus anti-resonant frequency
dependence of the effective materials parameters for a periodic array of thin
metallic wires with cuts placed periodically along the length of the wire, with
roles of the permittivity and permeability reversed from the SRR case. We show
in a simple manner that the finite unit cell size is responsible for the
anti-resonant behavior
Bose-Einstein condensation in a one-dimensional interacting system due to power-law trapping potentials
We examine the possibility of Bose-Einstein condensation in one-dimensional
interacting Bose gas subjected to confining potentials of the form , in which , by solving the
Gross-Pitaevskii equation within the semi-classical two-fluid model. The
condensate fraction, chemical potential, ground state energy, and specific heat
of the system are calculated for various values of interaction strengths. Our
results show that a significant fraction of the particles is in the lowest
energy state for finite number of particles at low temperature indicating a
phase transition for weakly interacting systems.Comment: LaTeX, 6 pages, 8 figures, uses grafik.sty (included), to be
published in Phys. Rev.
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