4,178 research outputs found
Radiation-hard ASICs for optical data transmission in the ATLAS pixel detector
We have developed two radiation-hard ASICs for optical data transmission in
the ATLAS pixel detector at the LHC at CERN: a driver chip for a Vertical
Cavity Surface Emitting Laser (VCSEL) diode for 80 Mbit/s data transmission
from the detector, and a Bi-Phase Mark decoder chip to recover the control data
and 40 MHz clock received optically by a PIN diode. We have successfully
implemented both ASICs in 0.25 um CMOS technology using enclosed layout
transistors and guard rings for increased radiation hardness. We present
results from prototype circuits and from irradiation studies with 24 GeV
protons up to 57 Mrad (1.9 x 10e15 p/cm2).Comment: 8th Tropical Seminar on Innovative Particle and Radiation Detectors,
Siena, Italy (2002
Superluminal Localized Solutions to Maxwell Equations propagating along a waveguide: The finite-energy case
In a previous paper of ours [Phys. Rev. E64 (2001) 066603, e-print
physics/0001039] we have shown localized (non-evanescent) solutions to Maxwell
equations to exist, which propagate without distortion with Superluminal speed
along normal-sized waveguides, and consist in trains of "X-shaped" beams. Those
solutions possessed therefore infinite energy. In this note we show how to
obtain, by contrast, finite-energy solutions, with the same localization and
Superluminality properties. [PACS nos.: 41.20.Jb; 03.50.De; 03.30.+p; 84.40.Az;
42.82.Et. Keywords: Wave-guides; Localized solutions to Maxwell equations;
Superluminal waves; Bessel beams; Limited-dispersion beams; Finite-energy
waves; Electromagnetic wavelets; X-shaped waves; Evanescent waves;
Electromagnetism; Microwaves; Optics; Special relativity; Localized acoustic
waves; Seismic waves; Mechanical waves; Elastic waves; Guided gravitational
waves.]Comment: plain LaTeX file (12 pages), plus 10 figure
Size-dependent permittivity and intrinsic optical anisotropy of nanometric gold thin films: A density functional theory study
Physical properties of materials are known to be different from the bulk at the nanometer scale. In this context, the dependence of optical properties of nanometric gold thin films with respect to film thickness is studied using density functional theory (DFT). We find that the in-plane plasma frequency of the gold thin film decreases with decreasing thickness and that the optical permittivity tensor is highly anisotropic as well as thickness dependent. Quantitative knowledge of planar metal film permittivity's thickness dependence can improve the accuracy and reliability of the designs of plasmonic devices and electromagnetic metamaterials. The strong anisotropy observed may become an alternative method of realizing indefinite media. © 2013 Optical Society of America
Superluminal X-shaped beams propagating without distortion along a coaxial guide
In a previous paper [Phys. Rev. E64 (2001) 066603; e-print physics/0001039],
we showed that localized Superluminal solutions to the Maxwell equations exist,
which propagate down (non-evanescence) regions of a metallic cylindrical
waveguide. In this paper we construct analogous non-dispersive waves
propagating along coaxial cables. Such new solutions, in general, consist in
trains of (undistorted) Superluminal "X-shaped" pulses. Particular attention is
paid to the construction of finite total energy solutions. Any results of this
kind may find application in the other fields in which an essential role is
played by a wave-equation (like acoustics, geophysics, etc.). [PACS nos.:
03.50.De; 41.20;Jb; 83.50.Vr; 62.30.+d; 43.60.+d; 91.30.Fn; 04.30.Nk; 42.25.Bs;
46.40.Cd; 52.35.Lv. Keywords: Wave equations; Wave propagation; Localized
beams; Superluminal waves; Coaxial cables; Bidirectional decomposition; Bessel
beams; X-shaped waves; Maxwell equations; Microwaves; Optics; Special
relativity; Coaxial metallic waveguides; Acoustics; Seismology; Mechanical
waves; Elastic waves; Guided gravitational waves.]Comment: plain LaTeX file (22 pages), plus 15 figures; in press in Phys. Rev.
Transformation Optics for Plasmonics
A new strategy to control the flow of surface plasmon polaritons at metallic
surfaces is presented. It is based on the application of the concept of
Transformation Optics to devise the optical parameters of the dielectric medium
placed on top of the metal surface. We describe the general methodology for the
design of Transformation-Optical devices for surface plasmons and analyze, for
proof-of-principle purposes, three representative examples with different
functionalities: a beam shifter, a cylindrical cloak and a ground-plane cloak.Comment: 15 pages, 3 figure
Gyrotropic impact upon negatively refracting surfaces
Surface wave propagation at the interface between different types of gyrotropic materials and an isotropic negatively refracting medium, in which the relative permittivity and relative permeability are, simultaneously, negative is investigated. A general approach is taken that embraces both gyroelectric and gyromagnetic materials, permitting the possibility of operating in either the low GHz, THz or the optical frequency regimes. The classical transverse Voigt configuration is adopted and a complete analysis of non-reciprocal surface wave dispersion is presented. The impact of the surface polariton modes upon the reflection of both plane waves and beams is discussed in terms of resonances and an example of the influence upon the Goos–Hänchen shift is given
Moulding the flow of surface plasmons using conformal and quasiconformal mapping
In this paper we analyze how Transformation Optics recipes can be applied to
control the flow of surface plasmons on metal-dielectric interfaces. We study
in detail five different examples: a cylindrical cloak, a beam shifter, a
right-angle bend, a lens and a ground-plane cloak. First, we demonstrate that
only the modification of the electric permittivity and magnetic permeability in
the dielectric side can lead to almost perfect functionalities for surface
plasmons. We also show that, thanks to the quasi two-dimensional character of
surface plasmons and its inherent polarization, the application of conformal
and quasiconformal mapping techniques allows the design of plasmonic devices in
which only the isotropic refractive index of the dielectric film needs to be
engineered.Comment: To be published in New Journal of Physic
Green's function for metamaterial superlens: Evanescent wave in the image
We develop a new method to calculate the evanescent wave, the subdivided
evanescent waves (SEWs), and the radiative wave, which can be obtained by
separating the global field of the image of metamaterial superlens. The method
is based on Green's function, and it can be applied in other linear systems.
This study could help us to investigate the effect of evanescent wave on
metamaterial superlens directly, and give us a new way to design new devices.Comment: 15 pages, 3 figure
Natural variation and dosage of the HEI10 meiotic E3 ligase control Arabidopsis crossover recombination
During meiosis, homologous chromosomes undergo crossover recombination, which creates genetic diversity and balances homolog segregation. Despite these critical functions, crossover frequency varies extensively within and between species. Although natural crossover recombination modifier loci have been detected in plants, causal genes have remained elusive. Using natural Arabidopsis thaliana accessions, we identified two major recombination quantitative trait loci (rQTLs) that explain 56.9% of crossover variation in ColxLer F2 populations. We mapped rQTL1 to semidominant polymorphisms in HEI10, which encodes a conserved ubiquitin E3 ligase that regulates crossovers. Null hei10 mutants are haploinsufficient, and, using genome-wide mapping and immunocytology, we show that transformation of additional HEI10 copies is sufficient to more than double euchromatic crossovers. However, heterochromatic centromeres remained recombination-suppressed. The strongest HEI10-mediated crossover increases occur in subtelomeric euchromatin, which is reminiscent of sex differences in Arabidopsis recombination. Our work reveals that HEI10 naturally limits Arabidopsis crossovers and has the potential to influence the response to selection
X-wave mediated instability of plane waves in Kerr media
Plane waves in Kerr media spontaneously generate paraxial X-waves (i.e.
non-dispersive and non-diffractive pulsed beams) that get amplified along
propagation. This effect can be considered a form of conical emission (i.e.
spatio-temporal modulational instability), and can be used as a key for the
interpretation of the out of axis energy emission in the splitting process of
focused pulses in normally dispersive materials. A new class of spatio-temporal
localized wave patterns is identified. X-waves instability, and nonlinear
X-waves, are also expected in periodical Bose condensed gases.Comment: 4 pages, 6 figure
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