456 research outputs found
Sub-wavelength imaging with a left-handed material flat lens
We study numerically, by means of the pseudospectral time-domain method, the
unique features of imaging by a flat lens made of a left-handed metamaterial
that possesses the property of negative refraction. We confirm the earlier
finding that a left-handed flat lens can provide near-perfect imaging of a
point source and a pair of point sources with clear evidence of the
sub-wavelength resolution. We illustrate the limitation of the resolution in
the time-integrated image due to the presence of surface waves.Comment: 4 pages, RevTeX, 6 figures; added references and some discussio
Finite-Difference and Pseudospectral Time-Domain Methods Applied to Backwards-Wave Metamaterials
Backwards-wave (BW) materials that have simultaneously negative real parts of
their electric permittivity and magnetic permeability can support waves where
phase and power propagation occur in opposite directions. These materials were
predicted to have many unusual electromagnetic properties, among them
amplification of the near-field of a point source, which could lead to the
perfect reconstruction of the source field in an image [J. Pendry, Phys. Rev.
Lett. \textbf{85}, 3966 (2000)]. Often systems containing BW materials are
simulated using the finite-difference time-domain technique. We show that this
technique suffers from a numerical artifact due to its staggered grid that
makes its use in simulations involving BW materials problematic. The
pseudospectral time-domain technique, on the other hand, uses a collocated grid
and is free of this artifact.
It is also shown that when modeling the dispersive BW material, the linear
frequency approximation method introduces error that affects the frequency of
vanishing reflection, while the auxiliary differential equation, the Z
transform, and the bilinear frequency approximation method produce vanishing
reflection at the correct frequency. The case of vanishing reflection is of
particular interest for field reconstruction in imaging applications.Comment: 9 pages, 8 figures, accepted by IEEE Transactions on Antennas and
Propagatio
Bistable diode action in left-handed periodic structures
We study nonlinear transmission of an asymmetric multilayer structure created
by alternating slabs of two materials with positive and negative refractive
index. We demonstrate that such a structure exhibits passive spatially
nonreciprocal transmission of electromagnetic waves, the analogue of the
electronic diode. We study the properties of this left-handed diode and confirm
its highly nonreciprocal and bistable transmittance by employing direct
simulations.Comment: 4 pages, 5 figure
Muslim Women in Interfaith Partnerships in Germany
The number of Muslim-interfaith couples in European countries has become significant due to transnational migration and a growing number of Muslims living in Muslim Minority countries. While the challenges for partners in such unions are complex, this article focuses on the lived experiences of Muslim women in interfaith intimate relationships in Germa ny. Drawing on field interviews with women in mixed-faith relationships, the following questions are central: How do Muslim women conceptualize religious identity and practices? Do they face challenges from different groups (Muslim communities, their families, friends, etc.) and if so, how do these challenges manifest? If respondents create concepts of being Muslim for themselves, how do these evolve in their narratives? How do they question, adapt or discard theological and social demands? Preliminary results illustrate that some respondents would appreciate a Muslim community that accepts their positionality as intermarried Muslim women. Looking at the narration of religious practices and concepts of Muslimness in the interviews, it becomes clear that a classification as haram, or legally forbidden, puts a simple categorical bar in front of a socially and theologically complex context. The inquiry combines interview analysis with situational mapping and is informed by Grounded Theory methodology.Peer Reviewe
Tunable transmission and bistability in left-handed bandgap structures
We study the defect-induced nonlinear transmission of a periodic structure
created by alternating slabs of two materials with positive and negative
refractive index. We demonstrate bistable switching and tunable nonlinear
transmission in a novel type of bandgap that corresponds to the vanishing
average refractive index, and compare the observed effects for two types of the
bandgaps.Comment: 3 pages, 5 figures; significant change
The Zero-n Gap Soliton
Periodic structures consisting of alternating layers of positive index and
negative index materials possess a novel band gap at the frequency at which the
average refractive index is zero. We show that in the presence of a Kerr
nonlinearity, this zero-n gap can switch from low transmission to a perfectly
transmitting state, forming a nonlinear resonance or gap soliton in the
process. This zero-n gap soliton is omnidirectional in contrast to the usual
Bragg gap soliton of positive index periodic structure
Wave scattering by metamaterial wedges and interfaces
We outline specific features of numerical simulations of metamaterial wedges
and interfaces. We study the effect of different positioning of a grid in the
Yee method, which is necessary to obtain consistent convergence in modeling of
interfaces with metamaterials characterized by negative dielectric permittivity
and negative magnetic permeability. We demonstrate however that, in the
framework of the continuous-medium approximation, wave scattering on the wedge
may result in a resonant excitation of surface waves with infinitely large
spatial frequencies, leading to non-convergence of the simulation results that
depend on the discretization step.Comment: 12 pages, 9 figure
- …