Efficiency of dispersive wave generation in dual concentric core microstructured fiber

We describe the generation of powerful dispersive waves that are observed when pumping a dual concentric core microstructured fiber by means of a sub-nanosecond laser emitting at the wavelength of~1064 nm. The presence of three zeros in the dispersion curve, their spectral separation from the pump wavelength, and the complex dynamics of solitons originated by the pump pulse break-up, all contribute to boost the amplitude of the dispersive wave on the long-wavelength side of the pump. The measured conversion efficiency towards the dispersive wave at 1548 nm is as high as 50%. Our experimental analysis of the output spectra is completed by the acquisition of the time delays of the different spectral components. Numerical simulations and an analytical perturbative analysis identify the central wavelength of the red-shifted pump solitons and the dispersion profile of the fiber as the key parameters for determining the efficiency of the dispersive wave generation process.Comment: 11 pages, 12 figure

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Q-switching of a microchip laser by means of a plasma

Présentation orale : ULTRA/NANO-7-27-4International audienc

Q-switching of a microchip laser using a plasma prism

International audienceWe demonstrate a novel method for active and passive Q-switching of a bulk laser source. The mechanism is based on the deflection of laser light through an electric channel of plasma that is temporarily created inside the resonator. The channel of plasma consists of an electric spark in air actuated with a spark gap. It acts as a spatio-temporal prism that momentarily enables the laser light to oscillate resonantly, thus triggering the creation of a laser pulse. Nanosecond pulses from a microchip laser source have been obtained with a limited timing jitter

Microlaser impulsionnel à déclenchement par plasma

Poster 43National audienc

Compact supercontinuum sources and their biomedical applications

International audienceRecent developments of compact white-light supercontinuum laser sources are reviewed. Basically these sources make use of a sub-nanosecond microchip laser and a photonic crystal fiber, leading to spectral broadening in the ultraviolet, visible and infrared ranges. The applicability of such supercontinuum sources to the biomedical field is introduced, with the demonstration of promising results in flow cytometry, CARS microscopy and optical coherence tomography. Their attractive benefits in terms of size, robustness, stability and cost are highlighted

Controlling intermodal four-wave mixing from the design of microstructured optical fibers

International audienceIntermodal four-wave mixing (FWM) in microstructured optical fibers (MOF) is studied theoretically and experimentally. The dependance of FWM frequency detuning on the geometrical parameters of the fiber, namely the pitch, the core width and the air-filling fraction is derived. We propose to use the results of this investigation to control the position of the Stokes and anti-Stokes waves directly from the fiber transverse structure drawing without the need for time-consuming simulations as in usual design procedures. Stokes sideband can then be freely tuned within the S-, L-, and C- bands with great potential for infrared applications

New Biomedical Opportunities Offered by Compact Sub-Nanosecond Supercontinuum Sources

International audienc

Guidage à faibles pertes d'un rayonnement ultra-violet à l'aide d'une fibre optique microstructurée à coeur creux

National audienc