71 research outputs found
Light Engineering of the Polariton Landscape in Semiconductor Microcavities
We demonstrate a method to create potential barriers with polarized light
beams for polaritons in semiconductor microcavities. The form of the barriers
is engineered via the real space shape of a focalised beam on the sample. Their
height can be determined by the visibility of the scattering waves generated in
a polariton fluid interacting with them. This technique opens up the way to the
creation of dynamical potentials and defects of any shape in semiconductor
microcavities.Comment: 4 pages, 5 figure
Fractional oscillator process with two indices
We introduce a new fractional oscillator process which can be obtained as
solution of a stochastic differential equation with two fractional orders.
Basic properties such as fractal dimension and short range dependence of the
process are studied by considering the asymptotic properties of its covariance
function. The fluctuation--dissipation relation of the process is investigated.
The fractional oscillator process can be regarded as one-dimensional fractional
Euclidean Klein-Gordon field, which can be obtained by applying the Parisi-Wu
stochastic quantization method to a nonlocal Euclidean action. The Casimir
energy associated with the fractional field at positive temperature is
calculated by using the zeta function regularization technique.Comment: 32 page
Relaxation bottleneck and its suppression in semiconductor microcavities
A polariton relaxation bottleneck is observed in angle-resolved measurements of photoluminescence emission from a semiconductor microcavity. For low power laser excitation, low k polariton states are found to have a very small population relative to those at high k. The bottleneck is found to be strongly suppressed at higher powers in the regime of superlinear emission of the lower polariton states. Evidence for the important role of carrier-carrier scattering in suppression of the bottleneck is presented
All -optical control of the quantum flow of a polariton condensate
Although photons in vacuum are massless particles that do not appreciably interact with each other, significant interactions appear in suitable nonlinear media, leading to hydrodynamic behaviours typical of quantum fluids(1-6). Here, we show the generation and manipulation of vortex-antivortex pairs in a coherent gas of strongly dressed photons (polaritons) flowing against an artificial potential barrier created and controlled by a light beam in a semiconductor microcavity. The optical control of the polariton flow allows us to reveal new quantum hydrodynamical phenomenologies such as the formation of vortex pairs upstream from the optical barrier, a case of ultra-short time excitation of the quantum flow, and the generation of vortices with counterflow trajectories. Additionally, we demonstrate how to permanently trap and store quantum vortices hydrodynamically generated in the wake of a defect. These observations are supported by time-dependent simulations based on the non-equilibrium Gross-Pitaevskii equation(7)
Models and measurements for the transmission of submicron-width waveguide bends defined in two-dimensional photonic crystals
Towards a LED based on a photonic crystal nanocavity for single photon sources at telecom wavelength
A fundamental step towards achieving an "on demand" single photon source would be the possibility of electrical pumping for a single QD and thus the integration of such a device in an opto-electronic circuit. In this work we describe the fabrication process and preliminary results of a Light Emitting Diode (LED) to be integrated with a PhC nanocavity at telecom wavelength. We demonstrate the possibility of an effective electric pumping of the QDs embedded into the membrane by contacting the n-doped and p-doped layers of the thin membrane, which allows the fabrication of a PhC nanocavity on it. (C) 2007 Elsevier B.V. All rights reserved
Polariton superfluids reveal quantum hydrodynamic solitons
A quantum fluid passing an obstacle behaves differently from a classical one.
When the flow is slow enough, the quantum gas enters a superfluid regime and
neither whirlpools nor waves form around the obstacle. For higher flow
velocities, it has been predicted that the perturbation induced by the defect
gives rise to the turbulent emission of quantised vortices and to the
nucleation of solitons. Using an interacting Bose gas of exciton-polaritons in
a semiconductor microcavity, we report the transition from superfluidity to the
hydrodynamic formation of oblique dark solitons and vortex streets in the wake
of a potential barrier. The direct observation of these topological excitations
provides key information on the mechanisms of superflow and shows the potential
of polariton condensates for quantum turbulence studies.Comment: Published version with corrected colorbar scale for Fig. 3. Raw data
available as ancillary file
Near-field mapping of quantum dot emission from single-photonic crystal cavity modes
We directly investigate, by means of near-field spectroscopy, the spatial distribution of the optical cavity modes of 2D photonic crystal microcavities. Numerical simulations confirm that the photoluminescence maps of quantum dots embedded in the photonic structure qualitatively match the spatial modulation of the electric field intensity. (C) 2007 Elsevier B.V. All rights reserved
Expansion and isoperimetric constants for product graphs
International audienceVertex and edge isoperimetric constants of graphs are studied. Using a functional-analytic approach, the growth properties, under products, of these constants is analyzed
- …