15th International Conference on Ultrafast Phenomena, 2006
ABSTRACT The amplitude of light diffracted in the near field by micrometric spherical silica bead... more ABSTRACT The amplitude of light diffracted in the near field by micrometric spherical silica beads shows caustics named photonic jets. To demonstrate their presence, we performed a femtosecond two-photon excited photoluminescence experiment with 4-Methylumbelliferone.
Si nanocrystals were formed in synthetic opals by Si-ion implantation and their optical propertie... more Si nanocrystals were formed in synthetic opals by Si-ion implantation and their optical properties studied using microphotoluminescence and reflection techniques. The properties of areas with high crystalline quality are compared with those of disordered regions of samples. The photoluminescence spectrum from Si nanocrystals embedded in silica spheres is narrowed by the inhibition of emission at wavelengths corresponding to the opal photonic pseudoband gap (∼690 nm). Measurements of photoluminescence spectra from individual implanted silica spheres is also demonstrated and the number of emitting Si nanocrystals in single brightly emitting spheres is estimated to be of the order of one thousand.
We report on a process to design highly ordered monolayers of two-dimensional photonic crystals, ... more We report on a process to design highly ordered monolayers of two-dimensional photonic crystals, made of silica nanoparticules, that can be used for the development of organic optical devices. We have used a photopolymerization process to incorporate a dye gain medium into the nanoparticle layers in order to achieve a laser cavity. The high spatial coherence of the deposits allows for single-mode laser emission in the plane of the layer when the light excitation is perpendicular to the plane. Such periodic films should help in reducing the number of layers needed for future electrically pumped distributed feedback lasers.
ABSTRACT We point out theoretically and experimentally the possibility to enhance a non-linear ef... more ABSTRACT We point out theoretically and experimentally the possibility to enhance a non-linear effect by using photonic jets. The new possibility to highly concentrate visible light with micrometric dielectric spheres is illustrated simulating the situation in water. The photonic jet is a highly energetic beam with special properties that deviate from geometrical optics. Its ability to enhance non-linear effects is experimentally demonstrated by studying the two-photon excited fluorescence of rhodamine B.
Since a decade photonic band gap research is expanding quickly and especially with self-assembled... more Since a decade photonic band gap research is expanding quickly and especially with self-assembled silica beads, called opals. However, a lot of problems are arising in their preparation, in particular the difficulty to produce large frequencies band gaps in common (periodic) silica photonic materials. To solve this problem quasiperiodic opals are known to be good candidates. Actually, the high degree
Abstract The first example of anion doped high Tc material Nd2CuO4−xFx was recently discovered by... more Abstract The first example of anion doped high Tc material Nd2CuO4−xFx was recently discovered by James, Zahurak et al. In order to increase the amount of superconducting material we used new preparation routes. A two step process was used: preparation of T Nd2CuO4 and Pr2CuO4 phases and then fluorination. The preparation of T' rare earth cuprates used are: oxides, hydroxide, oxalic and propionate synthesis method. The fluorination was done by reaction with NH4F under neutral gas. Using the previous way, large diamagnetism signal was observed as well on Nd2CuO4−xFx as on Pr2CuO4−xFx. X-ray and magnetic studies show as evidence an improvement of compounds.
The two-photon excited fluorescence from a dye solution is enhanced when a small amount of micro-... more The two-photon excited fluorescence from a dye solution is enhanced when a small amount of micro-meter sized silica beads are added. This observation is made in the simple scattering regime (inter-sphere distance four times larger than their radius) and is shown to depend on the concentration of the silica spheres. For a solution of rhodamine B, the enhancement can reach
ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has b... more ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has been investigated using Fourier Transform Infrared Spectroscopy (FT-IR). Palladium nanoparticles have been obtained by ultrasonic irradiation of Pd(NO(3))(2) solution in presence of ethylene glycol (EG) and PVP. The sonochemical reduction process of palladium ions (Pd(II)) to palladium atoms (Pd(0)) can be explained by considering the intense ultrasonic waves that are strong enough to produce cavitation: formation, growth and collapse of bubbles. The UV-Visible absorption spectroscopy revealed that the reduction of Pd (II) to metallic Pd has been successfully achieved. The FT-IR spectroscopy spectra analysis show that, in presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The transmission electron microscopy (HRTEM) and electron-dispersive X-ray (EDX) results confirm the dispersion, the nanometric size and the composition of the obtained palladium particles. (C) 2009 Elsevier B.V. All rights reserved
Since a decade photonic band gap research is expanding quickly and especially with self-assembled... more Since a decade photonic band gap research is expanding quickly and especially with self-assembled silica beads, called opals. However, a lot of problems are arising in their preparation, in particular the difficulty to produce large frequencies band gaps in common (periodic) silica photonic materials. To solve this problem quasiperiodic opals are known to be good candidates. Actually, the high degree
Two-photon Excited Microscopy (TPEM) and Electron Microscopy (EM) became in the past few years ro... more Two-photon Excited Microscopy (TPEM) and Electron Microscopy (EM) became in the past few years routine techniques for biological research, available in most imaging platforms, allowing in depth studies at organ or cellular level with TPEM and subcellular level with EM. Recently the combination of these two techniques is of growing emphasis, allowing the acquisition at these two scales on the same sample. The development of this correlative technique pointed out the necessity to engineer new dyes allowing the induction of contrast in both methods on the same system. We describe here the preparation and characterization of core shell iron oxide nanoparticles (for EM contrast) conjugated to new functionalized two-photon sensitive fluorescent dyes (for TPEM contrast). These dyes showed astonishing contrast in EM and TPEM on HeLa cell cultures.
15th International Conference on Ultrafast Phenomena, 2006
ABSTRACT The amplitude of light diffracted in the near field by micrometric spherical silica bead... more ABSTRACT The amplitude of light diffracted in the near field by micrometric spherical silica beads shows caustics named photonic jets. To demonstrate their presence, we performed a femtosecond two-photon excited photoluminescence experiment with 4-Methylumbelliferone.
Si nanocrystals were formed in synthetic opals by Si-ion implantation and their optical propertie... more Si nanocrystals were formed in synthetic opals by Si-ion implantation and their optical properties studied using microphotoluminescence and reflection techniques. The properties of areas with high crystalline quality are compared with those of disordered regions of samples. The photoluminescence spectrum from Si nanocrystals embedded in silica spheres is narrowed by the inhibition of emission at wavelengths corresponding to the opal photonic pseudoband gap (∼690 nm). Measurements of photoluminescence spectra from individual implanted silica spheres is also demonstrated and the number of emitting Si nanocrystals in single brightly emitting spheres is estimated to be of the order of one thousand.
We report on a process to design highly ordered monolayers of two-dimensional photonic crystals, ... more We report on a process to design highly ordered monolayers of two-dimensional photonic crystals, made of silica nanoparticules, that can be used for the development of organic optical devices. We have used a photopolymerization process to incorporate a dye gain medium into the nanoparticle layers in order to achieve a laser cavity. The high spatial coherence of the deposits allows for single-mode laser emission in the plane of the layer when the light excitation is perpendicular to the plane. Such periodic films should help in reducing the number of layers needed for future electrically pumped distributed feedback lasers.
ABSTRACT We point out theoretically and experimentally the possibility to enhance a non-linear ef... more ABSTRACT We point out theoretically and experimentally the possibility to enhance a non-linear effect by using photonic jets. The new possibility to highly concentrate visible light with micrometric dielectric spheres is illustrated simulating the situation in water. The photonic jet is a highly energetic beam with special properties that deviate from geometrical optics. Its ability to enhance non-linear effects is experimentally demonstrated by studying the two-photon excited fluorescence of rhodamine B.
Since a decade photonic band gap research is expanding quickly and especially with self-assembled... more Since a decade photonic band gap research is expanding quickly and especially with self-assembled silica beads, called opals. However, a lot of problems are arising in their preparation, in particular the difficulty to produce large frequencies band gaps in common (periodic) silica photonic materials. To solve this problem quasiperiodic opals are known to be good candidates. Actually, the high degree
Abstract The first example of anion doped high Tc material Nd2CuO4−xFx was recently discovered by... more Abstract The first example of anion doped high Tc material Nd2CuO4−xFx was recently discovered by James, Zahurak et al. In order to increase the amount of superconducting material we used new preparation routes. A two step process was used: preparation of T Nd2CuO4 and Pr2CuO4 phases and then fluorination. The preparation of T' rare earth cuprates used are: oxides, hydroxide, oxalic and propionate synthesis method. The fluorination was done by reaction with NH4F under neutral gas. Using the previous way, large diamagnetism signal was observed as well on Nd2CuO4−xFx as on Pr2CuO4−xFx. X-ray and magnetic studies show as evidence an improvement of compounds.
The two-photon excited fluorescence from a dye solution is enhanced when a small amount of micro-... more The two-photon excited fluorescence from a dye solution is enhanced when a small amount of micro-meter sized silica beads are added. This observation is made in the simple scattering regime (inter-sphere distance four times larger than their radius) and is shown to depend on the concentration of the silica spheres. For a solution of rhodamine B, the enhancement can reach
ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has b... more ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has been investigated using Fourier Transform Infrared Spectroscopy (FT-IR). Palladium nanoparticles have been obtained by ultrasonic irradiation of Pd(NO(3))(2) solution in presence of ethylene glycol (EG) and PVP. The sonochemical reduction process of palladium ions (Pd(II)) to palladium atoms (Pd(0)) can be explained by considering the intense ultrasonic waves that are strong enough to produce cavitation: formation, growth and collapse of bubbles. The UV-Visible absorption spectroscopy revealed that the reduction of Pd (II) to metallic Pd has been successfully achieved. The FT-IR spectroscopy spectra analysis show that, in presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The transmission electron microscopy (HRTEM) and electron-dispersive X-ray (EDX) results confirm the dispersion, the nanometric size and the composition of the obtained palladium particles. (C) 2009 Elsevier B.V. All rights reserved
Since a decade photonic band gap research is expanding quickly and especially with self-assembled... more Since a decade photonic band gap research is expanding quickly and especially with self-assembled silica beads, called opals. However, a lot of problems are arising in their preparation, in particular the difficulty to produce large frequencies band gaps in common (periodic) silica photonic materials. To solve this problem quasiperiodic opals are known to be good candidates. Actually, the high degree
Two-photon Excited Microscopy (TPEM) and Electron Microscopy (EM) became in the past few years ro... more Two-photon Excited Microscopy (TPEM) and Electron Microscopy (EM) became in the past few years routine techniques for biological research, available in most imaging platforms, allowing in depth studies at organ or cellular level with TPEM and subcellular level with EM. Recently the combination of these two techniques is of growing emphasis, allowing the acquisition at these two scales on the same sample. The development of this correlative technique pointed out the necessity to engineer new dyes allowing the induction of contrast in both methods on the same system. We describe here the preparation and characterization of core shell iron oxide nanoparticles (for EM contrast) conjugated to new functionalized two-photon sensitive fluorescent dyes (for TPEM contrast). These dyes showed astonishing contrast in EM and TPEM on HeLa cell cultures.
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Papers by J. Rehspringer