Corning (France)

We present a detailed overview of stimulated Brillouin scattering (SBS) in single-mode optical fibers. The review is divided into two parts. In the first part, we discuss the fundamentals of SBS. A particular emphasis is given to analytical calculation of the backreflected power and SBS threshold (SBST) in optical fibers with various index profiles. For this, we consider acousto-optic interaction in the guiding geometry and derive the modal overlap integral, which describes the dependence of the Brillouin gain on the refractive index profile of the optical fiber. We analyze Stokes backreflected power initiated by thermal phonons, compare values of the SBST calculated from different approximations, and discuss the SBST dependence on the fiber length. We also review an analytical approach to calculate the gain of Brillouin fiber amplifiers (BFAs) in the regime of pump depletion. In the high-gain regime, fiber loss is a nonnegligible effect and needs to be accounted for along with the pump depletion. We provide an accurate analytic expression for the BFA gain and show results of experimental validation. Finally, we review methods to suppress SBS including index-controlled acoustic guiding or segmented fiber links. The second part of the review deals with recent advances in fiber-optic applications where SBS is a relevant effect. In particular, we discuss the impact of SBS on the radio-over-fiber technology, enhancement of the SBS efficiency in Raman-pumped fibers, slow light due to SBS and SBS-based optical delay lines, Brillouin fiber-optic sensors, and SBS mitigation in high-power fiber lasers, as well as SBS in multimode and microstructured fibers. A detailed derivation of evolutional equations in the guided wave geometry as well as key physical relations are given in appendices.

Photonic crystal planar circuits designed and fabricated in silicon on silicon dioxide are demonstrated. Our structures are based on two-dimensional confinement by photonic crystals in the plane of propagation, and total internal reflection to achieve confinement in the third dimension. These circuits are shown to guide light at 1550 nm around sharp corners where the radius of curvature is similar to the wavelength of light.

Rectification, inversion, modulation, harmonic generation , and heterodyning are all effects well known in the world of electronics as the essential properties of practical devices. These, and many other, related, effects have applications in optics, made possible by te development of the laser, a source of intense monochromatic light. In this article, from the viewpoint of the materials scientist, the basic phenomena and their applications are presented before and various materials in use in nonlinear optics are discussed.

Polymer-layered silicate nanocomposites have drawn a great interest in polymer science these past years. Understanding of the complex mechanism of dispersion and exfoliation of the clay tactoids may allow us to better control the final morphology and the homogeneity of clay nanocomposites and thus their macroscopic properties. The first step we propose in this study consists of a multiscale approach of the exfoliation state of the extruded polypropylene/montmorillonite nanocomposite. We used three extruders designs: a single-screw extruder, a twin-screw extruder, and an optimized-screw extruder with adapted shear. The rheological analysis, the WAXS diffractograms, and the TEM micrographs all show different nanocomposite morphologies. A statistical TEM image analysis methodology was developed to evaluate the different particle parameters (thickness, length, aspect ratio, interparticle distance). The results obtained show a correlation between the size of the tactoids and the shear intensity.

Numerous relationships have been proposed in the literature to interpret wettability in terms of solid and liquid surface free energies. In the classical approach based on surface free energy components, the energy of interactions between the liquid and the solid is obtained from the geometric mean of the dispersion and polar contributions of the liquid and solid surface free energies. In this work, it is shown that the surface polarity of polar liquids can be modeled by the interaction of aligned permanent dipoles. A good agreement is found between the surface polarity characterized by polar component of the surface free energy of polar liquids (water, formamide and ethylene glycol) and the dipolar energy of interactions calculated from their dipole moment. At the liquid/polymer interfaces, polar interactions are better described by a simple relationship of proportionality with the polar component of the liquid surface free energy. This observation leads us to evaluate the hypothesis of induced polar interactions at liquid/polymer interfaces, the surface polarity of the solid being induced by the polar liquid in contact with the solid surface. Thus, the variation of the contact angle of a series of polar and non-polar liquids on various polymer substrates appears to be in better agreement when compared to the classical description of permanent polar interactions, so that a surface polarizability is defined for polymers. Using the surface polarizability approach rather than the polar component for the solid surface, we find also that the dispersion (non-polar) component of the polymer surface free energy is obtained with a better confidence, especially by taking into account the contact angles of both non-polar and polar liquid probes, or even by considering only polar liquid probes.

We demonstrate that room temperature MeV ion irradiation of a glass containing copper oxide initiates nucleation of pure Cu clusters via the inelastic "electronic" component of the ion energy loss, when the latter is above a threshold value. The clusters grow under subsequent thermal annealing, following Lifshitz-Slyozov-Wagner kinetics. The decoupling of nucleation and growth is analogous to that occurring in the photographic process. It allows total control over the cluster density, average size, and size distribution.

A study of thermodynamic properties and structure of sodium borosilicate glasses with a range of pressure-temperature histories is presented. It is demonstrated how differences in the pressure-temperature path of the liquid during cooling may result in glasses with identical short-range structure and molar volume but different potential energies and, thus, different mid- or long-range structures. Rates of changes of molar volume, excess enthalpy, and boron coordination with changing fictive pressure and fictive temperature are reported. A structure-energy map is given, and paths for transitions under constant pressure, as well as between different pressures are shown. It is shown for pressures between atmospheric and $500\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}$ that similar rates of cooling produce similar relative variations in fictive temperature in boron coordination environment and in the potential energy as compared to a given reference state. These results indicate that the rate of configurational entropy generation is independent of pressure in this range.

The dispersion diagram of the leaky modes in the planar photonic crystal waveguide is experimentally obtained for the wavelengths from 1440 to 1590 nm. A small stop band, around wavelength 1500 nm, is detected. The experimentally obtained results are in very good agreement with our three-dimensional finite difference time domain calculations. Propagation losses of the leaky modes are estimated and we have found that they decrease as we approach the ministop band.

The spreading dynamics of non-Newtonian fluids, in wetting and dewetting modes, plays a key role in numerous applications in particular in coating, adhesive bonding, and printing. The very common case of the shear-thinning behavior has been considered in this study. The wetting dynamics has been studied by depositing sessile drops on glass slides. The dewetting kinetics has been evaluated by measuring the rate of growth of dry zones nucleated in an unstable liquid film formed on Teflon-coated glass slides. The spreading kinetics of a liquid on a rigid substrate is governed by viscous dissipation in the liquid, the capillary driving force being compensated for by the braking force resulting from viscous shearing in the liquid. In the case where the liquid is not Newtonian but shear-thinning or pseudoplastic, a deviation from the classical hydrodynamic theory (Newtonian behavior) for wetting is obviously observed, in particular a slower wetting kinetics corresponding to an apparent increase of the liquid viscosity as the spreading speed decreases. The shape, slightly nonspherical, of shear-thinning drops having a size smaller than the capillary length, is also simply interpreted, observing that the actual viscosity increases from the edge to the center of drops during wetting, near the solid surface. In the dewetting mode no drastic changes are observed when compared with the general behavior of Newtonian liquids. The rate of growth of dry zones nucleated in an unstable liquid film stays constant, as for Newtonian liquids, at least at the early stages of the growth of dry patches. The proposed adaptation of the hydrodynamic theory is supported by several experimental results concerning the kinetics of spreading in the wetting and dewetting modes. A good agreement is observed between the proposed theory and the results.

The synthesis of Ag nanoclusters in soda lime silicate glasses and silica was studied by optical absorption and electron spin resonance experiments under both low (gamma ray) and high (MeV ion) deposited energy density irradiation conditions. Both types of irradiation create electrons and holes whose density and thermal evolution---notably via their interaction with defects---are shown to determine the clustering and growth rates of Ag nanocrystals. We thus establish the influence of redox interactions of defects and silver (poly)ions. The mechanisms are similar to the latent image formation in photography: Irradiation-induced photoelectrons are trapped within the glass matrix, notably on dissolved noble metal ions and defects, which are thus neutralized (reverse oxidation reactions are also shown to exist). Annealing promotes metal atom diffusion, which, in turn, leads to cluster nuclei formation. The cluster density depends not only on the irradiation fluence but also---and primarily---on the density of deposited energy and the redox properties of the glass. Ion irradiation (i.e., large deposited energy density) is far more effective in cluster formation, despite its lower neutralization efficiency (from ${\mathrm{Ag}}^{+}$ to ${\mathrm{Ag}}^{0}$) as compared to gamma photon irradiation.

Abstract Hydrophobic and anti-rain surface treatments are increasingly used to treat various glass articles such as windscreens, windows, headlamps, wing mirrors, optical lenses, sunglasses, etc. To evaluate the efficiency and durability of these treatments, we determine the smallest volume or critical sliding volume, V c , of a water drop able to slide down spontaneously under gravity after having been deposited on a vertical treated, glass surface. The property of water repellency is considered to be better when V c , is smaller. In this paper, a new simplified theory to describe the capillary force retaining the water drops on an inclined plane is proposed and verified practically. The experimental method allows us to compare the efficiency and durability of a commercial anti-rain and of a Corning Inc. proprietary hydrophobic surface treatment for glass, both being based on silicone derivative chemistry. As defined in this paper, the critical sliding volume appears to be a practical parameter which may be used to characterize quantitatively the hydrophobicity of a solid surface.

Highly efficient and chemoselective singlet oxygen oxidation of unprotected methionine was performed in water using a continuous mesofluidic reactor. Sustainable process engineering and conditions were combined to maximize process efficiency and atom economy, with virtually no waste generation and safe operating conditions. Three water-soluble metal-free photosensitizers [Rose Bengal, Methylene Blue, and tetrakis(4-carboxyphenyl)porphyrin] were assessed. The best results were obtained with Rose Bengal (0.1 mol %) at room temperature under white light irradiation and a slight excess of oxygen. Process and reaction parameters were monitored in real-time with in-line NMR. Other classical organic substrates (α-terpinene and citronellol) were oxidized under similar conditions with excellent performances.

The relation between the macroscopic and the microscopic (lattice) strain response to external uniaxial stress has been investigated for porous ceramics. Analytical and finite element modeling (FEM) have been performed and neutron diffraction data on porous sintered alumina and extruded honeycomb SiC have been used to validate the theoretical approach. By FEM simulations, it is shown that in spite of the complex pore microstructure, shear stresses are small during uniaxial compression. Analytical modeling shows that while the average microscopic stress depends on the applied macroscopic stress only through the porosity p, the average microscopic strain depends on the macroscopic stress through the pore morphology factor m, as well. Novel relationships are proposed to describe this dependence. Analytical calculations and numerical modeling perfectly agree with each other, and both show good consistency with experiments. As predicted, it has been observed that the microscopic (diffraction) Young’s modulus does not depend on the pore morphology factor, and follows the rule-of-mixtures, while the microscopic Poisson’s ratio does not even depend on porosity, but is equal to the value for the dense material property. A practical implication of these findings is that it is not possible to attach a pore morphology factor to a material, unless the processing conditions are tailored to vary p without varying m. In fact, the different values of m found for the different porosities explain why many models can be used to rationalize the experimental data. With the proposed method, the factor m can be independently evaluated by the use of macro- and micro-elastic properties of the porous body. Analogously, the macroscopic elastic properties of the dense material can be obtained by macroscopic and microscopic values measured on the correspondent porous material.

Human mesenchymal stem cells (hMSCs) present an attractive target for cell therapy given their wide availability, immunomodulatory properties, and multipotent nature for differentiation into chondrocytes, osteocytes, and adipocytes. With the progression of hMSC clinical studies, there is an increasing demand for development of technologies that enable efficient cell scale-up into clinically relevant quantities. Commercial scale manufacturing of hMSCs will require a large surface area which is not cost effective with available two-dimensional culture vessels. Recent studies showed that microcarriers provide a three-dimensional culture environment suitable for hMSC expansion. Traditionally, biological coatings and/or serum-containing medium are required to facilitate hMSC attachment and expansion in dynamic conditions. These limitations may hinder the use of microcarriers as a scale-up technology for hMSC therapeutics, where cell products, and therefore patient safety, are more controlled with the use of xeno-free, defined culture conditions. Here we report the long term culture of hMSCs on novel synthetic Synthemax II microcarriers in two different xeno-free media. Cells were maintained over 40 days on sterile, ready-to-use microcarriers in spinner flasks with programmed agitation. hMSC expansion was obtained by addition of fresh beads without the need for enzymatic dissociation. We achieved a cumulative cell expansion of >10,000 fold, and cells retained normal hMSC phenotype, karyotype, and tri-lineage differentiation potential. To our knowledge, this report is the first example of long term culture of hMSCs on synthetic microcarriers in xeno-free, defined conditions.

Although continuous flow technology can facilitate the scale-up of photochemical processes it is not yet routinely implemented on production scale in the fine chemical industries. This can be attributed to additional challenges compared to thermal processes, mostly in the homogeneous irradiation of the flow reactor. Here, we detail the process of bringing a previously developed photochemical benzylic bromination, utilizing in situ bromine generation, from lab to pilot scale. The process setup is discussed in detail, alongside a comprehensive risk assessment and discussion of problems encountered in the investigation of key reaction parameters. Ultimately, an assay yield of 88% was obtained in 22 s irradiated residence time, resulting in a productivity of 4.1 kg h–1 (space-time yield = 82 kg L–1 h–1) representing a 14-fold scale-up versus the lab-scale process.

Diazomethane is a valuable derivatizing agent but very difficult to handle for large-scale chemical transformations. We report here the base-induced decomposition of N-methyl-N-nitrosourea under continuous-flow conditions that enables the production up to 19 mol d–1 of diazomethane, at a total flow rate of 53 mL min–1.

The authors demonstrate the first ion-exchanged, planar lossless splitter at 1.5 µm. The 1 × 2 device was fabricated by thallium ion exchange in an Er/Yb codoped borosilicate glass, and achieved lossless splitting over the wavelength range 1534–1548 nm when pumped with a 980 nm laser diode.

Abstract A Grignard reaction performed in a microreactor is presented. The reaction is of type A (highly exothermic and very rapid) and has a low yield which is attributed to a hot spot formed in the mixing zone of the reactor. The reaction yield could be significantly increased by applying the multi‐injection principle, leading to better thermal control in the microreactor. Nevertheless, the microreactor plays a major role in reducing the magnitude of the hot spot. Knowing this, it was possible to design and construct an industrial microreactor with significant advantages such as modularity, high flow rate operation, and low investment expenditure (pumps and flow controller minimization).

Most living cells derived from solid tissues require an adhering surface to live in vitro conditions. A good understanding of the relationships between the behavior of cells and the physicochemical properties of substrates such as the surface free energy, the surface polarity, the presence of functional groups and surface charges is of prime importance for the optimization of adhesion, spreading and proliferation of cells. Polystyrene and treated polystyrene surfaces were characterized by determining their surface free energies using wettability measurements. The knowledge of the surface properties of the culture substrates provides a good view of the influence of the substrate properties on cell adhesion. However, this study shows that it is not directly the surface free energy of materials that controls cell adhesion but rather the interfacial free energy between the culture medium and the substrate. The interfacial free energy between the culture medium and the solid surface controls the adsorption of serum components that may inhibit or promote cell adhesion. One of the components inhibiting cell adhesion is serum albumin. The results indicate that the adsorption of serum albumin is related to the interfacial free energy between the culture medium and the substrate. Hydrophilic substrates, such as plasma treated polystyrene substrates, have a lower interfacial free energy with water than hydrophobic polystyrene leading to a lower adsorption of proteins inhibiting cell adhesion. In addition, it is observed that there is a competition between proteins inhibiting (serum albumin) and proteins promoting cell adhesion (such as fibronectin).

Metallic or semiconductor nanocrystals produced by very different techniques often display size distributions whose limiting shape (e.g., after long annealing times) is self-preserving and close to lognormal. We briefly survey the diverse microscopic mechanisms leading to this behavior, and present an experimental study of its inception in the case of semiconducting nanocrystals synthesized by ion implantation in silica. This example shows how the ultimate lognormal distribution is related to the system's memory loss of initial nucleation and growth processes.