408 research outputs found
On Layered Stable Processes
Layered stable (multivariate) distributions and processes are defined and
studied. A layered stable process combines stable trends of two different
indices, one of them possibly Gaussian. More precisely, in short time, it is
close to a stable process while, in long time, it approximates another stable
(possibly Gaussian) process. We also investigate the absolute continuity of a
layered stable process with respect to its short time limiting stable process.
A series representation of layered stable processes is derived, giving insights
into both the structure of the sample paths and of the short and long time
behaviors. This series is further used for sample paths simulation.Comment: 22 pages, 9 figure
On Fractional Tempered Stable Motion
Fractional tempered stable motion (fTSm)} is defined and studied. FTSm has
the same covariance structure as fractional Brownian motion, while having tails
heavier than Gaussian but lighter than stable. Moreover, in short time it is
close to fractional stable L\'evy motion, while it is approximately fractional
Brownian motion in long time. A series representation of fTSm is derived and
used for simulation and to study some of its sample path properties.Comment: 25 pages, 6 figure
Bloch wave propagation in two-dimensional photonic crystals: Influence of the polarization
Transverse Magnetic (TM) and Transverse Electric (TE) optical Bloch waves are the generic solutions of Maxwell's equations in two-dimensional photonic crystals (2D-PhCs). We present an intuitive description of these waves based on their Fourier decomposition into series of electromagnetic waves. The properties of these electromagnetic waves as well as their contribution to the global energy and group velocity of the global Bloch wave are discussed for each polarization. This description provides a simple and intuitive method to understand dispersion and group velocity effects in 2D-PhC
Spin rings in bi-stable planar semiconductor microcavities
A unique feature of exciton-polaritons, inherited from their mixed
light-matter origin, is the strongly spin-dependent polariton-polariton
interaction, which has been predicted to result in the formation of spin rings
in real space [Shelykh et al., Phys. Rev. Lett. 100, 116401 (2008)]. Here we
experimentally demonstrate the spin bi-stability of exciton-polaritons in an
InGaAs-based semiconductor microcavity under resonant optical pumping. We
observe the formation of spin rings whose size can be finely controlled in a
spatial scale down to the micrometer range, much smaller than the spot size. We
additionally evaluate the sign and magnitude of the antiparallel polariton spin
interaction constant.Comment: 5 pages, 4 figure
Polariton Squeezing in Semiconductor Microcavities
We report squeezed polariton generation using parametric polariton four-wave
mixing in semiconductor microcavities in the strong coupling regime. The
geometry of the experiment corresponds to degenerate four-wave mixing, which
gives rise to a bistability threshold. Spatial effects in the nonlinear regime
are evidenced, and spatial filtering is required in order to optimize the
measured squeezing. By measuring the noise of the outgoing light, we infer a 9
percent squeezing on the polariton field close to the bistability turning
point
Enhancement of Rabi Splitting in a Microcavity with an Embedded Superlattice
We have observed a large coupling between the excitonic and photonic modes of
an AlAs/AlGaAs microcavity filled with an 84-({\rm {\AA}})/20({\rm {\AA}})
GaAs/AlGaAs superlattice. Reflectivity measurements on the coupled
cavity-superlattice system in the presence of a moderate electric field yielded
a Rabi splitting of 9.5 meV at T = 238 K. This splitting is almost 50% larger
than that found in comparable microcavities with quantum wells placed at the
antinodes only. We explain the enhancement by the larger density of optical
absorbers in the superlattice, combined with the quasi-two-dimensional binding
energy of field-localized excitons.Comment: 5 pages, 4 figures, submitted to PR
Cathodoluminescence Mapping of Cherenkov-Radiation Generated Bloch-Modes in Planar Photonic Crystals by Fast Electrons
Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 - August 5, 201
Time-resolved optical characterization of InAs/InGaAs quantum dots emitting at 1.3 mu m
We present the time-resolved optical characterization of InAs/InGaAs self-assembledquantum dots emitting at 1.3 μm at room temperature. The photoluminescence decay time varies from 1.2 (5 K) to 1.8 ns (293 K). Evidence of thermalization among dots is seen in both continuous-wave and time-resolved spectra around 150 K. A short rise time of 10±2 ps is measured, indicating a fast capture and relaxation of carriers inside the dots
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