1,483 research outputs found
Tailoring the photonic bandgap of porous silicon dielectric mirror
A systematic method to fabricate porous silicon one dimensional photonic
crystals has been engineered to have a photonic bandwidth up to 2000nm. The
observation of the tailorability of the photonic bandgap (PBG) underscores the
requirement of the large refractive index contrast for making broad PBG
structures. In this letter, we present the fabrication and characteristics of
such structures that may be promising structures for a large variety of
applications.Comment: Published in Appl. Phys. Let
Bell inequality violation by entangled single photon states generated from a laser, a LED or a Halogen lamp
In single-particle or intraparticle entanglement, two degrees of freedom of a
single particle, e.g., momentum and polarization of a single photon, are
entangled. Single-particle entanglement (SPE) provides a source of non
classical correlations which can be exploited both in quantum communication
protocols and in experimental tests of noncontextuality based on the
Kochen-Specker theorem. Furthermore, SPE is robust under decoherence phenomena.
Here, we show that single-particle entangled states of single photons can be
produced from attenuated sources of light, even classical ones. To
experimentally certify the entanglement, we perform a Bell test, observing a
violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality. On the one
hand, we show that this entanglement can be achieved even in a classical light
beam, provided that first-order coherence is maintained between the degrees of
freedom involved in the entanglement. On the other hand, we prove that filtered
and attenuated light sources provide a flux of independent SPE photons that,
from a statistical point of view, are indistinguishable from those generated by
a single photon source. This has important consequences, since it demonstrates
that cheap, compact, and low power entangled photon sources can be used for a
range of quantum technology applications
Pump-and-probe optical transmission phase shift as a quantitative probe of the Bogoliubov dispersion relation in a nonlinear channel waveguide
We theoretically investigate the dispersion relation of small-amplitude
optical waves superimposing upon a beam of polarized monochromatic light
propagating along a single-mode channel waveguide characterized by an
instantaneous and spatially local Kerr nonlinearity. These small luminous
fluctuations propagate along the waveguide as Bogoliubov elementary excitations
on top of a one-dimensional dilute Bose quantum fluid evolve in time. They
consequently display a strongly renormalized dispersion law, of Bogoliubov
type. Analytical and numerical results are found in both the absence and the
presence of one- and two-photon losses. Silicon and silicon-nitride waveguides
are used as examples. We finally propose an experiment to measure this
Bogoliubov dispersion relation, based on a stimulated four-wave mixing and
interference spectroscopy techniques.Comment: 17 pages, 7 figure
High frequency electro-optic measurement of strained silicon racetrack resonators
The observation of the electro-optic effect in strained silicon waveguides
has been considered as a direct manifestation of an induced
non-linearity in the material. In this work, we perform high frequency
measurements on strained silicon racetrack resonators. Strain is controlled by
a mechanical deformation of the waveguide. It is shown that any optical
modulation vanishes independently of the applied strain when the applied
voltage varies much faster than the carrier effective lifetime, and that the DC
modulation is also largely independent of the applied strain. This demonstrates
that plasma carrier dispersion is responsible for the observed electro-optic
effect. After normalizing out free carrier effects, our results set an upper
limit of to the induced high-speed tensor
element at an applied stress of . This upper limit is about one
order of magnitude lower than the previously reported values for static
electro-optic measurements
Monte-Carlo simulations of the recombination dynamics in porous silicon
A simple lattice model describing the recombination dynamics in visible light
emitting porous Silicon is presented. In the model, each occupied lattice site
represents a Si crystal of nanometer size. The disordered structure of porous
Silicon is modeled by modified random percolation networks in two and three
dimensions. Both correlated (excitons) and uncorrelated electron-hole pairs
have been studied. Radiative and non-radiative processes as well as hopping
between nearest neighbor occupied sites are taken into account. By means of
extensive Monte-Carlo simulations, we show that the recombination dynamics in
porous Silicon is due to a dispersive diffusion of excitons in a disordered
arrangement of interconnected Si quantum dots. The simulated luminescence decay
for the excitons shows a stretched exponential lineshape while for uncorrelated
electron-hole pairs a power law decay is suggested. Our results successfully
account for the recombination dynamics recently observed in the experiments.
The present model is a prototype for a larger class of models describing
diffusion of particles in a complex disordered system.Comment: 33 pages, RevTeX, 19 figures available on request to
[email protected]
Hidden in plain sight: a massive, dusty starburst in a galaxy protocluster at z=5.7 in the COSMOS field
We report the serendipitous discovery of a dusty, starbursting galaxy at
(hereafter called CRLE) in close physical association with the
"normal" main-sequence galaxy HZ10 at . CRLE was identified by
detection of [CII], [NII] and CO(2-1) line emission, making it the highest
redshift, most luminous starburst in the COSMOS field. This massive, dusty
galaxy appears to be forming stars at a rate of at least 1500
yr in a compact region only kpc in diameter. The dynamical and
dust emission properties of CRLE suggest an ongoing merger driving the
starburst, in a potentially intermediate stage relative to other known dusty
galaxies at the same epoch. The ratio of [CII] to [NII] may suggest that an
important () contribution to the [CII] emission comes from a diffuse
ionized gas component, which could be more extended than the dense,
starbursting gas. CRLE appears to be located in a significant galaxy
overdensity at the same redshift, potentially associated with a large-scale
cosmic structure recently identified in a Lyman Alpha Emitter survey. This
overdensity suggests that CRLE and HZ10 reside in a protocluster environment,
offering the tantalizing opportunity to study the effect of a massive starburst
on protocluster star formation. Our findings support the interpretation that a
significant fraction of the earliest galaxy formation may occur from the inside
out, within the central regions of the most massive halos, while rapidly
evolving into the massive galaxy clusters observed in the local Universe.Comment: 16 pages, 9 figures, 4 tables, final version to appear on ApJ
(accepted May 19, 2018
Dynamical Characterization of Galaxies at z~4-6 via Tilted Ring Fitting to ALMA [CII] Observations
Until recently, determining the rotational properties of galaxies in the
early universe (z>4, Universe age <1.5Gyr) was impractical, with the exception
of a few strongly lensed systems. Combining the high resolution and sensitivity
of ALMA at (sub-) millimeter wavelengths with the typically high strength of
the [CII] 158um emission line from galaxies and long-developed dynamical
modeling tools raises the possibility of characterizing the gas dynamics in
both extreme starburst galaxies and normal star forming disk galaxies at z~4-7.
Using a procedure centered around GIPSY's ROTCUR task, we have fit tilted ring
models to some of the best available ALMA [CII] data of a small set of
galaxies: the MS galaxies HZ9 & HZ10, the Damped Lyman-alpha Absorber (DLA)
host galaxy ALMA J0817+1351, the submm galaxies AzTEC/C159 and COSMOS
J1000+0234, and the quasar host galaxy ULAS J1319+0950. This procedure directly
derives rotation curves and dynamical masses as functions of radius for each
object. In one case, we present evidence for a dark matter halo of O(10^11)
solar masses. We present an analysis of the possible velocity dispersions of
AzTEC/C159 and ULAS J1319+0950 based on matching simulated observations to the
integrated [CII] line profiles. Finally, we test the effects of observation
resolution and sensitivity on our results. While the conclusions remain limited
at the resolution and signal-to-noise ratios of these observations, the results
demonstrate the viability of the modeling tools at high redshift, and the
exciting potential for detailed dynamical analysis of the earliest galaxies, as
ALMA achieves full observational capabilities.Comment: 20 pages, 6 figures, Accepted for publication in Ap
Análisis y ejecución de estrategias en la industria de sensores mediante la simulación CAPSIM
Documento en el que se muestra el trabajo realizado en la dirección de una empresa de la industria de sensores dentro del simulador de negocios Capsim. Se presenta un análisis de la industria de los sensores, se describe la empresa en la que se trabajó, las estrategias de negocio y el proceso de su implementación, así como los resultados finales
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