Évaluation des pratiques professionnelles dans la prise en charge du traumatisme crânien grave avec monitorage de l’hémostase par Rotem dans le service de réanimation traumatologique du CHU de Dijon : étude préliminaire

Introduction La traumatologie crânienne grave reste une priorite en terme de sante publique avec une mortalite elevee ainsi que des sequelles importantes. Les troubles de l’hemostase associes peuvent aggraver le pronostic. Ils doivent etre corriger rapidement. L’objectif de notre travail est de realiser une evaluation des pratiques professionnelles de la prise en charge des patients traumatises crâniens graves au CHU de Dijon et d’observer les facteurs aggravant le pronostic, notamment les troubles de l’hemostase. Materiel et methodes Il a ete mene dans un premier temps une etude retrospective observationnelle de janvier 2011 a decembre 2013 sur l’ensemble des patients ayant ete hospitalise…

Optical addressing at the subwavelength scale

The Green dyadic formalism is applied to the study of the optical properties of dielectric subwavelength structures integrated in coplanar geometry. We first consider homogeneous wires with high refractive index featuring subwavelength cross sections. We show that such wires may have guiding properties and that they may be coupled with a local illumination produced by a focused Gaussian beam totally reflected at the substrate interface. When excited by the focused beam, these subwavelength optical waveguides (SOW's) provide a confined source of light that could be used to excite a single nanoscopic object. Well designed heteregeneous wires resulting from the alignment of dielectric particle…

Modelling Optical Resonators Probed by Subwavelength Sized Optical Detectors

The possibility of mapping the optical field structure inside a Fabry-Perot resonator by using a pointed optical fiber was recently reported [1]. In this contribution, we propose a simulation of such near-field optical experiments by using a two-dimensional self-consistent model. The method based on the discretization of four different domains, i.e. the two mirrors, the glass sample and the tip, allows us a meaningful description of the evolution of the full field pattern when approaching the optical detector. In particular, this computerized work supply a direct illustration of the optical energy tranfer occurring when the tip enters the near-field zone. In this context, different tip desi…

Spatiotemporal properties of nanoshell plasmonic response for strong-field experiments

International audience; Field enhancement behavior of a SiO 2 /Au nanoshell is studied in the framework of strong-field physics. Localized plasmonic fields induce local electric field enhancement with the potential to lead to the strong-field regime without the use of costly amplified lasers. In this framework, electrons are tunnel ionized from the nanoshell and accelerated by the local field being spatially inhomogeneous in terms of spectral and polarization properties. These processes are happening within a single laser shot, and thermal effects are therefore neglected. We show that the localized response to ultrashort femtosecond pulses can be investigated by extending Mie theory to mult…

Photonic transfer through subwavelength optical waveguides

Optical tunneling effect through dielectric junctions with subwavelength transverse sizes has been demonstrated some years ago. In this letter, we demonstrate how similar effects can be exploited to perform photonic transfer through a subwavelength optical wave guide (SOW) by structuring its optical index along the direction of propagation. The optical transmittance of the SOW is computed self-consistently in direct space through the numerical solution of a Dyson equation. We apply this scheme to investigate the optical properties of different SOW architectures. Even under total internal reflection, in which the light is coupled to the SOW by an evanescent mode, an efficient optical transfe…

Addressing and imaging high optical index dielectric ridges in the optical near field

Experimental observation of light coupling between ${\mathrm{TiO}}_{2}$ integrated waveguides of subwavelength cross section and pure three-dimensional evanescent light fields is reported. This near-field optical phenomenon is produced by controlling the location of the focusing of a laser beam totally reflected at the surface of the sample. The phenomenon is observed in direct space with a photon scanning tunneling microscope. Dielectric ridges several tens of micrometers long have been efficiently excited with this technique. Upon excitation, the extremities of the linear dielectric wires display intense light spots localized both inside and around the ridge. For ridge lengths up to $30\e…

Near-field observation of evanescent light wave coupling in subwavelength optical waveguides

International audience; We report the observation, in the range of visible frequencies, of the coupling of light into integrated waveguides of subwavelength cross-sections together with a subwavelength detection at the output, of such guides. Coupling in is produced by controlling the focusing of a laser beam totally reflected at the surface of the sample. Several tens of micrometres long dielectric ridges have been efficiently excited with this technique. The phenomenon is observed in direct space by a Photon Scanning Tunneling Microscope which also allows to test the principle of detection in a subwavelength volume.

Spatially resolved photonic transfer through mesoscopic heterowires

We report spatially resolved observations of light wave propagation along high refraction index dielectric heterowires lying on a transparent substrate. The heterowires are made of linear chains of closely packed mesoscopic particles. The optical excitation of these heterowires is performed through channel waveguides featuring submicrometer transverse cross sections. Both numerical simulations and near-field optical images, recorded with a photon scanning tunneling microscope, agree to show that, at visible frequencies, tuning the periodicity of the heterowires controls the propagation length within a range of several micrometers.

SUBWAVELENGTH OPTICAL DEVICES FOR NANOMETER SCALE APPLICATIONS

Recent progress in near-field optics instrumentation led to a new class of subwavelength optical experiments in which it is intended to use either the optical tunnel effect (OTE) or the lower mode based transmission (LMBT) in order to control the optical transfer between several delocalized detection or injection centers. This paper presents a panel of new theoretical and experimental results computed or observed near various dielectric or metallic patterns, linear, curved, or dashed, integrated in coplanar geometry. In particular, we demonstrate, how an efficient control of light evanescent waves can allow structures of subwavelength cross sections to be addressed.

Optical Near-Field Properties of Lithographically Designed Metallic Nanoparticles

ABSTRACTWe report on the experimental observation of localized surface plasmons sustained by small metallic particles using a photon scanning tunneling microscope (PSTM). The surface plasmons are excited in gold nanostructures tailored by electron beam lithography. The constant height operation of the PSTM allowed a direct comparison with theoretical computations of the distribution of the optical near-field intensity. Plasmon coupling above a chain of Au particles and electromagnetic energy transfer from a resonantly excited nanoparticle to a nanowire are demonstrated. Our experimental results appear to be in good agreement with theoretical computations based on the Green's Dyadic Techniqu…

Fluorescence relaxation in the near-field of a mesoscopic metallic particle : distance dependence and role of plasmon modes

International audience; We analytically and numerically analyze the fluorescence decay rate of a quantum emitter placed in the vicinity of a spherical metallic particle of mesoscopic size (i.e with dimensions comparable to the emission wavelength). We discuss the efficiency of the radiative decay rate and non–radiative coupling to the particle as well as their distance dependence. The electromagnetic coupling mechanisms between the emitter and the particle are investigated by analyzing the role of the plasmon modes and their nature (dipole, multipole or interface mode). We demonstrate that near-field coupling can be expressed in a simple form verifying the optical theorem for each particle …

Simultaneous observation of light localization and confinement in near-field optics

We report on the observation, in direct space, of both light localization and confinement effects near lithographically designed structures. The sample is observed in the optical near-field zone with a Photon Scanning Tunneling Microscope (PSTM). Several patterns composed of a few periods of TiO2 dots, arranged as a hexagonal lattice, have been investigated. When the central dot of the pattern is removed, a phenomenon of light localization above the vacancy can be observed in the PSTM image. The occurrence of this phenomenon can be related to the variation of the electromagnetic local density of state.

Progress in the interpretation of near-field optics

International audience

Direct observation of localized surface plasmon coupling

We report on the direct observation of localized surface plasmon coupling using a photon scanning tunneling microscope. The surface plasmons are excited in gold nanostructures tailored by electron beam lithography. Electromagnetic energy transfer from a resonantly excited nanoparticle to a nanowire, which is not directly excited by the incident light is observed. Our experimental results appear to be in good agreement with theoretical computations based on Green's dyadic technique.

Near‐field optical addressing of single molecules in coplanar geometry: a theoretical study

Photonic transfer through elongated optical structures of submicrometre section microfabricated at the surface of dielectric or semiconductor samples can be enhanced by an appropriate structuring of the local refraction index. We show from computerized simulations that both the light localization and the spectroscopic properties of such structures can be used to selectively excite, in coplanar geometry, individuals molecules located in the near-field.

Physics of Near-Field Optical Images

Construction, assembly and tests of the ATLAS electromagnetic barrel calorimeter

The construction and assembly of the two half barrels of the ATLAS central electromagnetic calorimeter and their insertion into the barrel cryostat are described. The results of the qualification tests of the calorimeter before installation in the LHC ATLAS pit are given.

SNOM signal near plasmonic nanostructures: an analogy with fluorescence decays channels

International audience; Scanning Near-field Optical Microscope (SNOM) is based on local excitations of nanostructures deposited on a substrate (illumination mode). Ideally, the local source behaves like a dipolar emitter so that the SNOM signal is strongly similar to the fluorescence decay rates of an excited molecule that would be located at the SNOM tip position. We present here how the SNOM signal near plasmonic nanostructures can be used to analyze radiative and non-radiative contribution to the fluorescence decay rate.

Subwavelength mapping of surface photonic states

We show that the spectral tailoring of optical local density of states (LDOS) may be achieved by lithographically designed nanostructures and that the subwavelength mapping of the spectral variation of the optical LDOS is feasible by varying the driving frequency of the effective dipole used in an illumination mode scanning near-field optical microscope.