1,701 research outputs found
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
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
Impairment of executive functions in a patient with a focal lesion in the anterior cingulate cortex. Evidence from neuropsychological assessment
Medicamentos e ingestión de alcohol: estudio del almotriptan
Diversos investigadors de l'Hospital Universitari Germans Trias i Pujol i de l'empresa farmacèutica Laboratorios Almirall han dut a terme un estudi per comprovar quin és l'efecte terapèutic de l'almotriptan -un fà rmac utilitzat en el tractament de les crisis de migranya- en relació al consum d'alcohol. Els resultats obtinguts en la recerca indiquen que no és necessari modificar la dosificació del medicament quan s'administra en un pacient en què la crisi de migranya s'ha produït després de la presa d'alcohol.Diversos investigadores del Hospital Universitario Germans Trias i Pujol y de la empresa farmacéutica Laboratorios Almirall han llevado a cabo un estudio para comprobar cuál es el efecto terapéutico del almotriptan - un fármaco utilizado en el tratamiento de las crisis de migraña- en relación al consumo de alcohol. Los resultados obtenidos en la investigación indican que no es necesario modificar la dosificación del medicamento cuando se administra en un paciente en que la crisis de migraña se ha producido después de la ingestión de alcohol
Impairment of executive functions in a patient with a focal lesion in the anterior cingulate cortex. Evidence from neuropsychological assessment
Sustainable cycle-tourism for society: Integrating multi-criteria decision-making and land use approaches for route selection
Cycle tourism is a sustainable active vacation, which is quickly growing in recent years. Although it has several benefits for society and users (e.g., social connections, amusement, and physical and mental health), cycle tourism requires an adequate route network to enjoy destinations with historical and landscape peculiarities. Past literature mainly investigated motivations and preferences for cycle tourists and proposed optimisation methods in planning routes. However, applying assessment methods for prioritising cycle-tourist routes is a seldom-explored topic. This study aims to address this gap by applying an integrated method for evaluating and prioritising cycle routes, searching for a compromise between route characteristics, service provided to users, and natural and building contexts crossed. It jointly includes Multi-Criteria Decision Methods (MCDMs) and a land use approach: AHP determines the weights of criteria and parameters describing cycle routes; GIS elaborates spatial analysis of parameters; ELECTRE I and VIKOR help find a compromise solution amongst different cycle routes. The integrated method involved a panel of experts to collect data, and it is applied to the wide-study area of Franciacorta (Italy). Some comparisons with other MCDMs are made to justify the results. The findings could support multi-institutions prioritising cycle route alternatives in deciding their building
Vacancy complexes in nonequilibrium germanium-tin semiconductors
Understanding the nature and behavior of vacancy-like defects in epitaxial
GeSn metastable alloys is crucial to elucidate the structural and
optoelectronic properties of these emerging semiconductors. The formation of
vacancies and their complexes is expected to be promoted by the relatively low
substrate temperature required for the epitaxial growth of GeSn layers with Sn
contents significantly above the equilibrium solubility of 1 at.%. These
defects can impact both the microstructure and charge carrier lifetime. Herein,
to identify the vacancy-related complexes and probe their evolution as a
function of Sn content, depth-profiled pulsed low-energy positron annihilation
lifetime spectroscopy and Doppler broadening spectroscopy were combined to
investigate GeSn epitaxial layers with Sn content in the 6.5-13.0 at.% range.
The samples were grown by chemical vapor deposition method at temperatures
between 300 and 330 {\deg}C. Regardless of the Sn content, all GeSn samples
showed the same depth-dependent increase in the positron annihilation line
broadening parameters, which confirmed the presence of open volume defects. The
measured average positron lifetimes were the highest (380-395 ps) in the region
near the surface and monotonically decrease across the analyzed thickness, but
remain above 350 ps. All GeSn layers exhibit lifetimes that are 85 to 110 ps
higher than the Ge reference layers. Surprisingly, these lifetimes were found
to decrease as Sn content increases in GeSn layers. These measurements indicate
that divacancies are the dominant defect in the as-grown GeSn layers. However,
their corresponding lifetime was found to be shorter than in epitaxial Ge thus
suggesting that the presence of Sn may alter the structure of divacancies.
Additionally, GeSn layers were found to also contain a small fraction of
vacancy clusters, which become less important as Sn content increases
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]
Reconfigurable optical routers based on Coupled Resonator Induced Transparency resonances.
The interferometric coupling of pairs of resonators in a resonator sequence generates coupled ring induced transparency (CRIT) resonances. These have quality factors an order of magnitude greater than those of single resonators. We show that it is possible to engineer CRIT resonances in tapered SCISSOR (Side Coupled Integrated Space Sequence of Resonator) to realize fast and efficient reconfigurable optical switches and routers handling several channels while keeping single channel addressing capabilities. Tapered SCISSORs are fabricated in silicon-on-insulator technology. Furthermore, tapered SCISSORs show multiple-channel switching behavior that can be exploited in DWDM applications
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