422 research outputs found
Adding SALT to Coupled Microcavities: the making of active photonic molecule lasers
A large body of work has accumulated over the years in the study of the
optical properties of single and coupled microcavities for a variety of
applications, ranging from filters to sensors and lasers. The focus has been
mostly on the geometry of individual resonators and/or on their combination in
arrangements often referred to as photonic molecules (PMs).
Our primary concern will be the lasing properties of PMs as ideal candidates
for the fabrication of integrated microlasers, photonic molecule lasers.
Whereas most calculations on PM lasers have been based on cold-cavity (passive)
modes, i.e. quasi-bound states, a recently formulated steady-state ab initio
laser theory (SALT) offers the possibility to take into account the spectral
properties of the underlying gain transition, its position and linewidth, as
well as incorporating an arbitrary pump profile. We will combine two
theoretical approaches to characterize the lasing properties of PM lasers: for
two-dimensional systems, the generalized Lorenz-Mie theory will obtain the
resonant modes of the coupled molecules in an active medium described by SALT.
Not only is then the theoretical description more complete, the use of an
active medium provides additional parameters to control, engineer and harness
the lasing properties of PM lasers for ultra-low threshold and directional
single-mode emission.Comment: 16th International Conference on Transparent Optical Networks (2014
The Fruit Fly as a Meeting Place for Microbes
Many infectious diseases of humans are caused by polymicrobial communities, but there are few in vivo models to study such communities. In a recent issue of PLoS Pathogens, Sibley and colleagues (Sibley et al., 2008a) report the development of a fruit fly infection model to investigate polymicrobial interactions and their effects on the host
Optimization of integrated polarization filters
This study reports on the design of small footprint, integrated polarization
filters based on engineered photonic lattices. Using a rods-in-air lattice as a
basis for a TE filter and a holes-in-slab lattice for the analogous TM filter,
we are able to maximize the degree of polarization of the output beams up to 98
% with a transmission efficiency greater than 75 %. The proposed designs allow
not only for logical polarization filtering, but can also be tailored to output
an arbitrary transverse beam profile. The lattice configurations are found
using a recently proposed parallel tabu search algorithm for combinatorial
optimization problems in integrated photonics
Ab initio investigation of lasing thresholds in photonic molecules
We investigate lasing thresholds in a representative photonic molecule
composed of two coupled active cylinders of slightly different radii.
Specifically, we use the recently formulated steady-state ab initio laser
theory (SALT) to assess the effect of the underlying gain transition on lasing
frequencies and thresholds. We find that the order in which modes lase can be
modified by choosing suitable combinations of the gain center frequency and
linewidth, a result that cannot be obtained using the conventional approach of
quasi-bound modes. The impact of the gain transition center on the lasing
frequencies, the frequency pulling effect, is also quantified
Femtosecond Self-Reconfiguration of Laser-Induced Plasma Patterns in Dielectrics
Laser-induced modification of transparent solids by intense femtosecond laser
pulses allows fast integration of nanophotonic and nanofluidic devices with
controlled optical properties. So far, the local and dynamic nature of the
interactions between plasma and light needed to correctly explain nanograting
fabrication on dielectric surfaces has been missing in the theoretical models.
With our numerical approach, we show that a self-consistent dynamic treatment
of the plasma formation and its interaction with light triggers an ultrafast
reconfiguration of the periodic plasma patterns on a field-cycle time scale.
Within this framework, a simple stability analysis of the local interactions
explains how the laser-induced plasma patterns change their orientation with
respect to the incident light polarization, when a certain energy density
threshold is reached. Moreover, the reconfigured sub-wavelength plasma
structures grow into the bulk of the sample and agree with the experimental
findings of self-organized volume nanogratings. Mode coupling of the incident
and transversally scattered light with the periodic plasma structures is
sufficient to initiate the growth and the self-organization of the
characteristic pattern with a periodicity of a half-wavelength in the medium.Comment: 8 pages, 7 figure
Pseudomonas aeruginosa in premise plumbing of large buildings.
International audiencePseudomonas aeruginosa is an opportunistic bacterial pathogen that is widely occurring in the environment and is recognized for its capacity to form or join biofilms. The present review consolidates current knowledge on P. aeruginosa ecology and its implication in healthcare facilities premise plumbing. The adaptability of P. aeruginosa and its capacity to integrate the biofilm from the faucet and the drain highlight the role premise plumbing devices can play in promoting growth and persistence. A meta-analysis of P. aeruginosa prevalence in faucets (manual and electronic) and drains reveals the large variation in device positivity reported and suggest the high variability in the sampling approach and context as the main reason for this variation. The effects of the operating conditions that prevail within water distribution systems (disinfection, temperature, and hydraulic regime) on the persistence of P. aeruginosa are summarized. As a result from the review, recommendations for proactive control measures of water contamination by P. aeruginosa are presented. A better understanding of the ecology of P. aeruginosa and key influencing factors in premise plumbing are essential to identify culprit areas and implement effective control measure
Quorum Sensing Controls Swarming Motility of Burkholderia glumae through Regulation of Rhamnolipids.
International audienceBurkholderia glumae is a plant pathogenic bacterium that uses an acyl-homoserine lactone-mediated quorum sensing system to regulate protein secretion, oxalate production and major virulence determinants such as toxoflavin and flagella. B. glumae also releases surface-active rhamnolipids. In Pseudomonas aeruginosa and Burkholderia thailandensis, rhamnolipids, along with flagella, are required for the social behavior called swarming motility. In the present study, we demonstrate that quorum sensing positively regulates the production of rhamnolipids in B. glumae and that rhamnolipids are necessary for swarming motility also in this species. We show that a rhlA- mutant, which is unable to produce rhamnolipids, loses its ability to swarm, and that this can be complemented by providing exogenous rhamnolipids. Impaired rhamnolipid production in a quorum sensing-deficient B. glumae mutant is the main factor responsible for its defective swarming motility behaviour
Modèle familial de la personne souffrant d'un premier épisode psychotique et intervention thérapeutique
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