Electrostriction and guidance of sound by light in optical fibers

We investigate the generation of phonon wavepackets in optical fibers via electrostriction from coherent optical waves. Solving the elastodynamic equation subject to the electrostrictive force, we are able to reproduce experimental spectra found in standard and photonic crystal fibers. We discuss the two important practical cases of forward interaction, dominated by elastic resonances of the fiber, and backward interaction, for which an efficient mechanism of phonon guidance by light is found. The latter result describes the formation of the coherent phonon wavepacket involved in stimulated Brillouin scattering

Generation of phonons from electrostriction in small-core optical waveguides

International audienceWe investigate the generation of acoustic phonons from electrostriction of optical waves in small core waveguides. We specifically consider simple step-index strip waveguides composed of silica or silicon in air, with sub-micron lateral dimensions. Such waveguides support one or a few optical modes, but a rich spectrum of acoustic phonons that becomes densely populated as the phonon frequency increases. We evaluate rigorously the phonon energy density that results from the electrostriction of two frequency detuned guided optical waves, that are either co- or contra-propagating, including phonon loss. Plotting this energy density as a function of frequency detuning reveals the phonon wave packets that are electrostrictively active and gives a quantitative estimation of the energy transfer from optical waves to particular phonons. Furthermore, in the backward interaction geometry, the dispersion relation of such phonons can be accessed directly by varying the optical wavelength

Plasma 5-hydroxyindoleacetic acid as an endogenous index of renal plasma flow

Plasma 5-hydroxyindoleacetic acid as an endogenous index of renal plasma flow. 5-Hydroxyindoleacetic acid (5-HIAA), the major serotonin metabolite, was measured in human plasma and urine using liquid chromatography and electrochemical detection. The renal extraction of 5-HIAA was 78%, a value compatible with an almost complete extraction during a single passage of the blood through the kidney. In addition, plasma levels of 5-HIAA measured in patients with a wide range of renal function was inversely correlated (r = 0.85) with the clearance of para-aminohippuric acid (PAH). The results indicate that 5-HIAA determinations can be used as an alternative procedure to the PAH clearance method for the estimation of renal plasma flow in clinical practice

Stimulated Brillouin scattering in hybrid chalcogenide-PMMA microwires

International audienceWe investigate the onset of nonlinear effects in hybrid As2Se3-PMMA microwires and demonstrate that they provide an enhanced Kerr nonlinearity while mitigating stimulated Brillouin scattering when compared to chalcogenide and silica optical fibers

Observation of surface acoustic wave Brillouin scattering in optical microfibers (Orale)

International audienceWe report the observation of surface-acoustic-wave Brillouin scattering (SAWBS) in a subwavelength-diameter fiber and show that this effect relies on the generation by the electrostrictive force of phonons confined at the surface of the microwire

Complete experimental characterization of stimulated Brillouin scattering in photonic crystal fiber

International audienceWe provide a complete experimental characterization of stimulated Brillouin scattering in a 160 m long solid-core photonic crystal fiber, including threshold and spectrum measurements as well as positionresolved mapping of the Brillouin frequency shift. In particular, a three-fold increase of the Brillouin threshold power is observed, in excellent agree-ment with the spectrally-broadened Brillouin gain spectrum. Distributed measurements additionally reveal that the rise of the Brillouin threshold results from the broadband nature of the gain spectrum all along the fiber and is strongly influenced by strain. Our experiments confirm that these unique fibers can be exploited for the passive control or the suppression of Brillouin scattering

The prion or the related Shadoo protein is required for early mouse embryogenesis

AbstractThe prion protein PrP has a key role in transmissible spongiform encephalopathies but its biological function remains largely unknown. Recently, a related protein, Shadoo, was discovered. Its biological properties and brain distribution partially overlap that of PrP. We report that the Shadoo-encoding gene knockdown in PrP-knockout mouse embryos results in a lethal phenotype, occurring between E8 and E11, not observed on the wild-type genetic background. It reveals that these two proteins play a shared, crucial role in mammalian embryogenesis, explaining the lack of severe phenotype in PrP-knockout mammals, an appreciable step towards deciphering the biological role of this protein family

Honeycomb Photonic Crystal Waveguides in a Suspended Silicon Slab

“© © 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”[EN] We report experimental evidence of light guiding at telecommunication wavelengths along line-defect honeycomb-lattice photonic crystal waveguides created in suspended silicon slabs. Numerical results show that the guided bands correspond to modes below the cladding light line so they are inherently lossless, although the measurements show quite high losses owing to fabrication imperfections. Honeycomb photonic crystals are a suitable platform for confining light and sound in nanoscale waveguides. © 1989-2012 IEEE.This work was supported by the EC Seventh Framework Programme (FP7/2007-2013) under Grant 233883 (TAILPHOX).Puerto Garcia, D.; Griol Barres, A.; Escalante Fernández, JM.; Pennec, Y.; Djafari-Rouhani, B.; Beugnot, J.; Laude, V.... (2012). Honeycomb Photonic Crystal Waveguides in a Suspended Silicon Slab. IEEE Photonics Technology Letters. 24(22):2056-2059. https://doi.org/10.1109/LPT.2012.2219516S20562059242