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Femtosecond pulse laser processing concentrates a huge quantity of light energy in extremely short pulses of a few tens to hundreds of femtoseconds, enabling superficial laser machining or marking of any kind of materials, with a reduced or insignificant heat affected area. A digitized paper printed image of the face on the Turin Shroud was used to monitor a scan head intercalated between a femtosecond pulsed laser source and a linen fabric sample, enabling the direct 2D reproduction of the image of the face with a laser beam size corresponding to one pixel of the digitized image. The contrast in the marked image was controlled by adjusting the energy density, the number of superimposed pulses per pixel, and the distance between successive impacts. The visual aspect of the laser-induced image is very similar, at naked eye, to the source image. The negative photograph of the marked linen fabric reveals a face remarkably close to the well-known negative picture of the face on the Turin Shroud. Analyses by infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy were performed to characterize the laser marked areas.

Hiding several images in a single printing, which appear selectively at different angles of observation, is of great interest for applications in security, data storage or design. Here, we propose an easy-to-implement ink-free laser-based technique to print nanostructured patterns that encode different grey-level images revealed to the eye at specific observation angles. The angular selectivity is provided by diffraction gratings whose orientation can be continuously controlled at the micrometer scale through self-organization mechanisms triggered by laser light. A diffraction yield allowing easy observation with the naked eye is demonstrated, thanks to the use of a thin TiO2:Ag film that also prevents damage to the substrates. The technology based on laser scanning is demonstrated on transparent and flexible substrates that do not sustain high temperature. This ink-free marking technology is flexible, suited to large surfaces, rapid, and provides unique visual effects on any kind of transparent substrate.

The Casimir effect is a force arising in the macroscopic world as a result of radiation pressure of vacuum fluctuations. It thus plays a key role in the emerging domain of nano-electro-mechanical systems (NEMS). This role is reviewed in the present paper, with discussions of the influence of the material properties of the mirrors, as well as the geometry dependence of the Casimir effect between corrugated mirrors. In particular, the lateral component of the Casimir force and restoring torque between metal plates with misaligned corrugations are evaluated.

L'existence de fluctuations irréductibles de champ dans le vide est une prédiction importante de la théorie quantique. Ces fluctuations ont de nombreuses conséquences observables comme l'effet Casimir, qui est maintenant mesuré avec une bonne précision et un bon accord avec la théorie, pourvu que celle-ci tienne compte des différences entre les expériences rélles et la situation idéale considérée par H.G.B. Casimir. Nous présenterons quelqu'unes des expériences récentes et discuterons les principales corrections à la force de Casimir liées à la situation expérimentale.

A process of creating controlled silver nanostructures using atomic force microscope technique is reported. The nanostructures are grown on both the silica surface and silica–indium-tin-oxide interface of a silver salt impregnated mesoporous silica film, deposited on indium tin oxide coated glass substrate. Voltage is applied between a conductive atomic force microscope tip and the indium tin oxide substrate to create the silver nanostructures. The possibility of switching the positions of the nanostructures between the silica film surface and the film–indium-tin-oxide interface, by reversing the electrical polarity of the tip, is demonstrated. It is also shown that the conductive channels can be created through the silica layer provided that the created metallic nanostructures are large enough to grow inside the film volume from one side to the other. The electrical conductivity of the film can be locally changed in a reversible manner by applying successively negative and positive voltages to the tip.

The transformation of three kinds of mesoporous films of amorphous TiO2under exposure to continuous wave (CW) lasers emitting at UV and visible wavelengths is investigated. Silver-free films, films impregnated with a silver salt, and films loaded with silver nanoparticles are considered. The silver containing films had previously been shown to exhibit a photochromic behavior. Intensity thresholds leading to laser-induced crystallization are evaluated using a combination of Raman spectroscopy, atomic force microscopy, and high-resolution electron microscopy. Crystallization in the anatase and rutile phases as well as ablation of the films are shown at 244 nm wavelength for increasing intensity, whatever the nature of the films. However, under visible light exposure, crystallization only occurs in the silver containing films. The oxidized-silver containing films, that are shown to be as transparent as the silver-free films in the visible range, appear to crystallize under visible light. The temperature rise occurring during visible light exposure and due to the plasmon-induced nanoparticle heating is measured. Finally, such a CW laser-induced crystallization is proven to be an accurate technique to produce permanent patterns with submicrometer widths and nanometer depths that can be tuned to within only a few nanometers. The patterns resist to temperature rises of 1000 °C.

The effect of auto‐ and heterotrophy on the carbon isotope composition (δ13C) of fatty acids (FA) and sterols was studied in the scleractinian coral Turbinaria reniformis. Colonies were maintained in aquaria for 6 weeks under two light levels (100 and 300 mmol photons m−2s−1) and/or two trophic conditions (starved and fed twice a week with zooplankton). In high‐light conditions, lipid biomarkers, both in the zooxanthellae and animal tissue, presented significantly higher δ13C values compared to those exposed to low light, supporting the widespread theory of enhanced 13C fixation with increasing irradiance and photosynthesis. This result and the similar lipid δ13C‐values of the host and the symbionts are a strong indication that most lipids are synthesized by the zooxanthellae. Feeding had a smaller effect than light on the lipid δ13C‐signatures and a more pronounced effect at low‐light level. Despite the depleted δ13C values of the zooplankton lipids, slight enrichment in 13C was observed in some FA from the host and zooxanthellae, whereas the main host sterol was depleted in 13C. These differences between FA and sterols give evidence for different biosynthesis pathways: FA might have been synthesized from the assimilation of carbohydrates or amino acids contained in the food, whereas sterols might derive from modification of dietary lipids.

Abstract.: The Casimir effect is a force arising in the macroscopic world as a result of radiation pressure of vacuum fluctuations. It thus plays a key role in the emerging domain of nano-electro-mechanical systems (NEMS). This role is reviewed in the present paper, with discussions of the influence of the material properties of the mirrors, as well as the geometry dependence of the Casimir effect between corrugated mirrors. In particular, the lateral component of the Casimir force and restoring torque between metal plates with misaligned corrugations are evaluated.

The Casimir effect is a force arising in the macroscopic world as a result of radiation pressure of vacuum fluctuations. It thus plays a key role in the emerging domain of nano-electro-mechanical systems (NEMS). This role is reviewed in the present paper, with discussions of the influence of the material properties of the mirrors, as well as the geometry dependence of the Casimir effect between corrugated mirrors. In particular, the lateral component of the Casimir force and restoring torque between metal plates with misaligned corrugations are evaluated.

A simple way to obtain a conducting nanocomposite is described, and the conducting particles are characterized. Core−shell particles [polystyrene−polyaniline (PANI)] have been obtained by the dispersion process from three types of polystyrene latexes: a no-cross-linked core stabilized by a nonylphenolethoxylate (NP40) and two cross-linked cores stabilized by NP40 and a mixture NP40/Surfamid (a surfactant bearing an amide group). The surface of these particles has been extensively characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and scanning electron microscopy. A maximum coverage of 94% was obtained for the high PANI content as revealed by XPS analysis. A better coverage was obtained for the cross-linked polystyrene latex stabilized by the Surfamid. The amide group of this surfactant allows the H-bonding formation with the PANI backbone and, thus, improves the conductivity. It was shown that a uniform coverage of the core particles was not required to ensure a good conductivity.

The relic gravitational wave background is expected to be statistically isotropic, but the actual value of the associated spacetime metric should break isotropy. We propose to detect the resulting anisotropy by using an optical interferometer mounted on a rotating platform.

Abstract:: We study the decoherence of atomic interferometers due to the scattering of stochastic gravitational waves. We evaluate the “direct” gravitational effect registered by the phase of the matter waves as well as the “indirect” effect registered by the light waves used as beam-splitters and mirrors for the matter waves. Considering as an example the space project HYPER, we show that both effects are negligible for the presently studied interferometers.

Phagocytic cells play a key role in the fish immune system. They secrete reactive oxygen species (ROS) involved in their bactericidal activity. These cells are highly sensitive to pollution by polycyclic aromatic hydrocarbons and other organic pollutants. We have investigated the intracellular mechanisms by which 3-methylcholanthrene (3-MC) increased bactericidal activity of carp phagocytes. Macrophages isolated from head kidney (pronephros) and incubated 1 h with 3-MC enhanced their production of ROS when they were stimulated 1.25 h with phorbol 12-myristate 13-acetate (PMA), a direct activator of protein kinase C (PKC). 3-MC also produced a rapid and a sustained increase in [Ca2+]i(2 h minimum). However, the cytochrome P450 1A and Ah receptor inhibitor, α-naphtoflavone (α-NF), inhibited the potentiation of PMA-induced ROS production, suggesting 3-MC metabolic activation. Moreover, α-NF increased [Ca2+]iwithout macrophage ROS production, suggesting that some mechanism other than calcium release is playing a role in the stimulation of the macrophages by 3-MC. The rise in [Ca2+]iinduced by 3-MC was potentiated by the inhibitor of the endoplasmic reticulum calcium ATPases, thapsigargin. And treating the cells with 3-MC decreased the calcium mobilization caused by thapsigargin. These results suggest that 3-MC acts on the endoplasmic reticulum, perhaps directly on calcium ATPases, to increase intracellular calcium levels in carp phagocytes.

Abstract: We study the influence of finite conductivity of metals on the Casimir effect. We put the emphasis on explicit theoretical evaluations which can help comparing experimental results with theory. The reduction of the Casimir force is evaluated for plane metallic plates. The reduction of the Casimir energy in the same configuration is also calculated. It can be used to infer the reduction of the force in the planesphere geometry through the “proximity theorem”. Frequency dependent dielectric response functions of the metals are represented either by the simple plasma model or, more accurately, by using the optical data known for the metals used in recent experiments, that is Al, Au and Cu. In the two latter cases, the results obtained here differ significantly from those published recently.

We present a quantum network approach to real high sensitivity measurements. Thermal and quantum fluctuations due to active as well as passive elements are taken into account. The method is applied to the analysis of the capacitive accelerometer using the cold damping technique, developed for fundamental physics in space by ONERA and the ultimate limits of this instrument are discussed. It is confirmed in this quantum analysis that the cold damping technique allows one to control efficiently the test mass motion without degrading the noise level.

Abstract:: We define quantum observables associated with Einstein localization in space-time. These observables are built on Poincaré and dilatation generators. Their commutators are given by spin observables defined from the same symmetry generators. Their shifts under transformations to uniformly accelerated frames are evaluated through algebraic computations in conformal algebra. Spin number is found to vary under such transformations with a variation involving further observables introduced as irreducible quadrupole momenta. Quadrupole observables may be dealt with as non commutative polarizations which allow one to define step operators increasing or decreasing the spin number by unity.

We review the schemes which have been implemented, in order to achieve quantum non-demolition (QND) measurements in the optical domain. The simplest schemes can be obtained using the optical Kerr effect, which yields a crossed-phase modulation coupling between two light beams. Other schemes use either independently generated squeezed light, or coupled-mode parametric amplifiers. These various schemes can be characterized using three criteria, which describe, respectively, the quality of the quantum measurement, the non-destruction of the signal, and the conditional variance of the output signal beam, given the output “meter” beam (quantum-state preparation criterion). We show that quantitative limits can be defined with respect to these criteria, delimiting “classical” and “quantum” domains of operation. Then we present in more detail a new experimental implementation of QND measurements, using three-level atoms inside a doubly-resonant optical cavity.

Abstract: It is shown that oscillators using nearly degenerate parametric conversion or four-wave mixing in the phase conjugation geometry generate pairs of highly correlated photons. The intensity difference of the two corresponding light beams is then expected to be below the shot noise limit. This property can be used to produce intensity stabilized light beams below the quantum limit. The phases of the twin beams also exhibit interesting correlation properties which will be discussed. Moreover, the combination of the twin beams gives a squeezed state, which has been observed by other authors when the device is below the oscillation threshold. We will describe preliminary results of experiments performedabove oscillation threshold.

Abstract:: We calculate the photon emission of a high finesse cavity moving in vacuum. The cavity is treated as an open system. The field initially in the vacuum state accumulates a dephasing depending on the mirrors motion when bouncing back and forth inside the cavity. The dephasing is not linearized in our calculation, so that qualitatively new effects like pulse shaping in the time domain and frequency up-conversion in the spectrum are found. Furthermore we predict the existence of a threshold above which the system should show self-sustained oscillations.

We describe how a two-mode, above-threshold, optical parametric oscillator can generate nonclassical states of light with a large average number of photons: the fluctuation spectrum of the various fields is calculated, and several quantities are shown to have squeezed fluctuations. In particular, a perfect quantum noise suppression is predicted on the difference between the intensities of the two generated beams. We describe an experiment designed to demonstrate such an effect and show how it can be used to generate high-intensity amplitude-squeezed states.

Laser-cooled and trapped cesium atoms have been used as a nonlinear medium in a nearly resonant cavity. A study of the semiclassical dynamics of the system was performed, showing bistability and instabilities. In the quantum domain, squeezing in a probe beam having interacted with this system was demonstrated.

We calculate by the semiclassical method the noise spectra of a non-degenerate optical parametric oscillator operating above threshold when taking into account two independent diffusion processes on the pump phase and on the signal-idler phase difference. We also show that the phase diffusion processes are important when calculating the quantum noise in an optical parametric oscillator for noise frequencies close to the beat frequency between the signal and idler modes.

La présence de fluctuations irréductibles de champ dans le vide est une prédiction importante de la théorie quantique. Ces fluctuations ont de nombreux effets bien connus, dont l'archétype est la force de Casimir apparaîssant entre deux miroirs placés dans le vide par suite de la pression de radiation du vide. Elle a été récemment mesurée avec une précision de l'ordre du %. De nombreux travaux sont consacrés à l'évaluation théorique de cette force en visant une précision du même ordre. Ici nous étudions la force de Casimir dans la configuration de deux miroirs métalliques plans parallèles à température nulle. En supposant les miroirs décrits par un modèle plasma nous interprétons la force de Casimir comme le résultat de l'interaction entre les plasmons de surface des deux miroirs.

Les modèles cosmologiques prévoient l'existence d'un fond d'ondes gravitationnelles à des fréquences très basses. Bien que ce fond soit statistiquement isotrope, la valeur effectivement prise pour la métrique d'espace-temps associée doit briser l'isotropie. Nous pensons que cette anisotropie peut être détectée en utilisant un détecteur d'onde gravitationnelle en rotation. Nous rediscutons dans ce contexte les expériences de test d'isotropie de la vitesse de la lumière.

Les tests récents de l'effet Casimir affichent une précision de l'ordre du pour-cent. Pour rendre compte des différences entre ces expériences réelles et la situation idéale de Casimir il faut disposer d'une théorie précise. C'est à cette fin que nous calculons la force et l'énergie de Casimir où les effets correctifs de la conductivité finie des miroirs et des fluctuations thermiques sont pris en compte simultanément. Ceci contraste avec l'approximation usuelle qui considèrent ces deux effets indépendamment l'un de l'autre en multipliant simplement entre elles leurs corrections respectives. Il s'avère que cette approximation, comparée à notre résultat exact, induit justement une erreur de l'ordre du pour-cent.

We investigate the effects of three reduction processes on the formation of silver nanoparticles in mesoporous titania films. The later are impregnated with silver salt and then either exposed to UV laser light, chemically treated or annealed. Depending on the reduction process, the NP are confined inside the mesopores or not, leading to different NP size distributions and to various film colors. These TiO2/Ag nanocomposite films also exhibit different photochromic behaviours when exposed to visible laser radiations. We characterize and interpret the color changes as well as the NP deformation and oxidation under visible illuminations.

The effect of vinylene carbonate (VC) as electrolyte additive on the formation mechanisms of passivation films covering both electrodes in lithium-ion batteries was investigated by X-ray photoelectron spectroscopy (XPS). LiCoO2/graphite coin cells using a LiPF6/ethylene carbonate:diethyl carbonate:dimethyl carbonate liquid electrolyte with or without VC were charged at 20 and 60°C. The identification of VC-derived products formed at the surface of the electrodes was carried out by a dual experimental/theoretical approach. From a classical XPS core peak analysis completed by a detailed interpretation and simulation of valence spectra supported by ab initio calculations, and through direct synthesis of the VC polymer, we could evidence the formation of the radical poly(VC) at the electrode/electrolyte interfaces. We showed that the radical polymerization is the main reaction mechanism of VC contributing to the formation of the passivation layers at the surface of both electrodes.