Sapphire planar waveguides fabricated by H+ ion beam implantation

1.1-MeV proton-implanted sapphire waveguides are investigated for the first time. Optical measurements show that the planar waveguides support low-order transverse-mode propagation with good guiding properties without the need to anneal the samples

Proton implanted sapphire planar and channel waveguides

We report low-order transverse-mode planar waveguides in sapphire fabricated for the first time by proton implantation. The waveguides show good guiding properties without post-implantation annealing. Channel waveguiding was achieved by polyimide strip-loading

Designable buried waveguides in sapphire by proton implantation

Buried and stacked planar as well as buried single and parallel channel waveguides are fabricated in sapphire by proton implantation. Good control of the implantation parameters provides excellent confinement of the guided light in each structure. Low propagation losses are obtained in fundamental-mode, buried channel waveguides without postimplantation annealing. Choice of the implantation parameters allows one to design mode shapes with different ellipticity and/or mode asymmetry in each orthogonal direction, thus demonstrating the versatility of the fabrication method. Horizontal and vertical parallelization is demonstrated for the design of one- or two-dimensional waveguide arrays in hard crystalline materials

Super-quadratic behavior of luminescence decay excited by energy-transfer upconversion

For several decades, energy-transfer upconversion (ETU) in rare-earth-ion doped systems [1,2] has attracted much attention, firstly, because of the fundamental interest in the physical nature of this process and, secondly, because of very practical considerations, namely the demonstration of near-infrared pumped visible light sources and, in reverse, the detrimental influence of ETU on the efficiency of infrared emitting systems.\ud We investigate fundamentally the behavior of infrared luminescence emitted directly from a metastable level and visible luminescence emitted after ETU from this level to higher-lying levels. Although these two luminescences are connected by the same metastable level and influenced by the same ETU process, the infrared luminescence probes all ions, while the visible luminescence probes only the class of ions susceptible to ETU [3]. A simple analytical model [4] predicts that such luminescence decay curves exhibit a super-quadratic dependence of upconversion on direct luminescence decay.\ud The Nd3+ ion can serve as a model system for such investigations. It exhibits strong ETU from the metastable 4F3/2 level. When doped into oxide matrices, the 4F3/2 level is the only metastable level. The Nd3+ energy levels excited by ETU decay by fast multiphonon relaxation and, hence, the weak visible fluorescence emitted from these levels represents a quasi instantaneous reaction on the dynamics of the 4F3/2 level. Experimental results obtained after pulsed laser excitation of Nd3+-doped oxide host materials show indeed a super-quadratic behavior of upconversion versus direct luminescence decay, in accordance with the model predictions [4].\ud \ud [1] F. Auzel, Proc. IEEE 1973, 6, 758\ud [2] J.C. Wright, Top. Appl. Phys. 1976, 15, 239\ud [3] M. Pollnau, D.R. Gamelin, S.R. Lüthi, H.U. Güdel, M.P. Hehlen, Phys. Rev. B 2000, 61, 3337\ud [4] M. Pollnau, J. Alloys Compd. 2002, 341, 5

Superquadratic behavior of upconversion luminescence transients in rare-earth-ion doped laser crystals

Inhomogeneous active-ion distributions in laser materials lead to strong deviations of upconversion versus direct luminescence transients from the quadratic law of energy-transfer upconversion. Measured luminescence decay curves in LaSc3(BO3)4:Nd3+ and GdVO4:Nd3+ confirm experimentally the predicted deviations. Differences in energy migration within the metastable level of Nd3+ are identified

L'utilisation de l'hypnose dans la prise en charge de la douleur du grand brûlé: travail de Bachelor

Le système de santé actuel met l’accent sur une médecine curative onéreuse et particulièrement basée sur l’innovation technologique. L’hypnose est une pratique ayant fait ses preuves dans le traitement de la douleur dans divers contextes de soins. Elle se révèle peu coûteuse, pouvant favoriser une diminution des traitements antalgiques et du séjour d’hospitalisation. Les brûlures comptent parmi les lésions les plus douloureuses et traumatiques. La gestion de l’antalgie est complexe et souvent inadéquate malgré un traitement médicamenteux conséquent. L’hypnothérapie en complément du traitement peut ainsi permettre une optimisation de la gestion de l’antalgie.L’objectif principal de ce travail de Bachelor est d’identifier les différentes composantes de la douleur dans le but de mesurer les effets de l’hypnose sur l’antalgie chez les grands brûlés. Ce travail vise également à déterminer si l’efficacité de l’hypnose est comparable à d’autres interventions non pharmacologiques et ainsi susciter une réflexion concernant les pratiques alternatives chez les professionnels de la santé. Ce travail est conduit sous forme d’une revue de la littérature étoffée afin de présenter l’état actuel des connaissances sur notre problématique et ainsi répondre à nos objectifs de départ. L’hypnose a des nombreux effets bénéfiques sur les composantes de la douleur telles que la douleur nociceptive et « affective ». Leur intensité est diminuée et s’accompagne également d’une diminution de l’anxiété et des traitements médicamenteux administrés. L’état actuel des connaissances ne permet pas d’affirmer avec certitude que l’hypnose est supérieure en termes d’antalgie à d’autres interventions non pharmacologiques. Néanmoins, il en découle des études retenues que l’hypnose serait la méthode alternative de premier choix dans le traitement de la douleur chez le grand brûlé. L’hypnothérapie, de par son approche holistique, a non seulement prouvé son efficacité sur l’antalgie mais également sur la qualité de vie du patient et sur son interaction avec les professionnels de la santé. Ces derniers ont ainsi un rôle important à jouer dans l’information et la promotion de pratiques complémentaires à notre médecine actuelle. Cette revue de la littérature prouve l’efficacité et l’efficience de l’hypnose tant pour le patient que pour les infirmiers. Néanmoins, la conduite de nouvelles études approfondissant le sujet permettrait de renforcer les connaissances actuelles afin d’appuyer l’utilisation de l’hypnose en milieu hospitalier

High pressure and high temperature in situ X-ray diffraction studies in the Paris-Edinburgh cell using a laboratory X-ray source

International audienceWe have developed a new laboratory experimental set-up to study in situ the pressure-temperature phase diagram of a given pure element or compound, its associated phase transitions, or the chemical reactions involved at high pressure and high temperature (HP-HT) between different solids and liquids. This new tool allows laboratory studies before conducting further detailed experiments using more brilliant synchrotron X-ray sources or before kinetic studies. This device uses the diffraction of X-rays produced by a quasi-monochromatic micro-beam source operating at the silver radiation (λ(Ag)Kα1,2 ≈ 0.56Å). The experimental set-up is based on a VX Paris-Edinburgh cell equipped with tungsten carbide or sintered diamond anvils and uses standard B-epoxy 5 or 7mm gaskets. The diffracted signal coming from the compressed (and heated) sample is collected on an image plate. The pressure and temperature calibrations were performed by diffraction, using conventional calibrants (BN, NaCl and MgO) for determination of the pressure, and by crossing isochores of BN, NaCl, Cu or Au for the determination of the temperature. The first examples of studies performed with this new laboratory set-up are presented in the article: determination of the melting point of germanium and magnesium under HP-HT, synthesis of MgB2 or C-diamond and partial study of the P, T phase diagram of MgH2

Production of hydrogen by borohydride: in search of low cost non-noble efficient catalyst

Hydrogen production by sodium borohydride through hydrolysis in alkaline solutions has been extensively studied as a production/storage option due to the high volumetric and gravimetric efficiency exhibited. The potential application of this option is based on an easily controllable catalysed hydrolysis reaction, non-toxic and recyclable by-products, and the high purity hydrogen produced can be used in fuel cells. This work reports on a comparative study of own-developed, supported and non-supported, nonnoble catalyst. Ru based catalysts are taken as reference. Characterization of the catalyst was accomplished using a FEG-SEM scanning electron microscope and FTIR analysis. Obtained values amount to 10 NLmin-1g-1 for Ni-based catalyst while Ru-based catalyst amount to twice as much in the same experimental conditions. Typical solutions contain sodium borohydride of concentrations between 2 and 10 wt%, stabilized with 3 to 10 wt % NaOH. Produced hydrogen is measured at ambient pressure as a function of catalyst exposure time at controlled temperatures till completion of the reaction. A thorough study of the open literature rendered normalized values for the reaction rate with different catalyst, making comparisons valuable

Dependence of upconversion on direct luminescence decay in energy-transfer upconversion

For several decades, energy-transfer upconversion (ETU) in rare-earth-ion doped systems [1,2] has attracted much attention, firstly, because of the fundamental interest in the physical nature of this process and, secondly, because of very practical considerations, namely the demonstration of near-infrared pumped visible light sources and, in reverse, the detrimental influence of ETU on the efficiency of infrared emitting systems. We investigate fundamentally the behavior of and interaction between infrared luminescence emitted directly from a metastable level and visible luminescence emitted after ETU from this metastable level to higher-lying levels. Although these two luminescences are connected by the same metastable level and influenced by the same ETU process, they probe different classes of ions. Whereas the infrared luminescence probes all ions, the visible luminescence probes only the class of ions susceptible to ETU [3]. A simple analytical model [4] predicts that such luminescence decay curves exhibit a super-quadratic dependence of upconversion on direct luminescence decay. The fraction of ions susceptible to ETU can be derived from this model. The Nd3+ ion can serve as a model system for such investigations. It exhibits strong ETU from the metastable 4F3/2 level. When doped into oxide matrices, the 4F3/2 level is the only metastable level within the 4f subshell. The Nd3+ energy levels excited by ETU decay by fast multiphonon relaxation and, hence, the weak visible fluorescence emitted from these levels represents a quasi instantaneous reaction on the dynamics of the 4F3/2 metastable level. Experimental results obtained after pulsed laser excitation of Nd3+-doped oxide host materials show indeed a super-quadratic behavior of upconversion versus direct luminescence decay, in accordance with the model predictions [4]. [1] F. Auzel, Proc. IEEE 6, 758 (1973) [2] J.C. Wright, Top. Appl. Phys. 15, 239 (1976) [3] M. Pollnau, D.R. Gamelin, S.R. Lüthi, H.U. Güdel, M.P. Hehlen, Phys. Rev. B 61, 3337 (2000) [4] M. Pollnau, J. Alloys Compd. 341, 51 (2002

Coherent broadband light source for parallel optical coherence tomography

A Ti:sapphire planar waveguide is rib structured by Ar ion milling to provide parallel channel waveguides. By coupling high-power pump light through a microlens array into the waveguides, a novel broadband luminescent parallel emitter is demonstrated as a light source for parallel optical coherence tomography using smart detector arrays