The development of the cube texture has been investigated in a Fe-50%Ni alloy undergoing recrystallization and normal grain growth by means of orientation imaging microscopy (OIMTM) and bulk texture measurements (X-ray diffraction). It is shown that both the oriented nucleation and the oriented growth mechanisms are responsible for the strengthening of the cube texture in the early stages of recrystallization in this alloy. The increase in the cube texture in the intermediate stages of recrystallization is mainly related to the high differentials in stored energy associated with cube grains. These experimental results are corroborated by way of a Monte-Carlo simulation of recrystallization based on data derived by OIM of the investigated alloy at its earliest recrystallization stages. The primary mechanism responsible for the development of the cube texture during grain growth relies on the preferential migration of the high-angle grain boundaries linked to cube grains which results from the advantage in number and size shown by cube grains when recrystallization is complete.

Large Angle Convergent Beam Electron Diffraction (LACBED) experiments on dislocations located in the mirror planes of icosahedral AlPdMn single grains show that – as previously inferred from standard image contrast technique – the direction of the Burgers vector is perpendicular to the mirror plane of movement, thus confirming the fact that climb should be an important process for the plasticity mechanisms in icosahedral quasicrystals.

Slanted chiral sculptured thin films (STFs) are introduced as nano-engineered materials that are effectively periodic in two orthogonal directions. Their periodicities normal and parallel to the substrate plane are related by a slant angle. A coupled wave theory is formulated and implemented for the planewave response of a slanted chiral STF of finite thickness. Numerical results show that the nonspecular remittances and the Rayleigh-Wood anomalies due to periodicity parallel to the substrate plane are tightly coupled to the specular nature of the circular Bragg phenomenon displayed due to periodicity normal to the substrate plane. In the Bragg regime, the left- and the right-circularly polarized components of the incident plane wave are redirected in non-trivially different directions. The potential of slanted chiral STFs as narrowband circular polarization beamsplitters is established.

We present experimental results on longitudinal magneto-optic Kerr effect in composite systems based on thin Fe layers associated with amorphous alumina (Al2O3). [Al2O3/Fe]m-samples ($m=1,\,2$) have been prepared by rf magnetron sputtering onto Si(100) substrate. We have investigated the effect of the Al2O3 and Fe thicknesses on the Kerr rotation. The geometry of the multilayers is predicted theoretically by using deduced experimental magneto-optical constants. It will be shown how large Kerr rotation values can be obtained by adjusting sample parameters. For instance, a Kerr rotation close to 7° has been observed from an Al2O3/Fe/Al2O3/Fe/Si multilayer. The reflectivity and the figure of merit are discussed as a function of the Al2O3 thickness.

New instrumentation has been developed that is dedicated to the measurement of surface morphology with high resolutions and short acquisition times. Sinusoidal phase-shifting interferometry is demonstrated to provide within an acquisition time of only a few milliseconds topographic images with ~1 nm height precision, ~1 μm lateral resolution, and a few tens of pm sensitivity. A white-light scanning microscope is also under development, using an in-house developed high speed, intelligent CCD camera, the first tests of which demonstrate the feasibility of providing topographic images of deep surface relief (several microns to several tens of microns) within less than 0.3 s. The useful lateral field of view can be extended by employing image “stitching” while maintaining a high lateral resolution. 


The aim of model reduction is to obtain the simplest model while reflecting as far as possible the dynamic behaviour of a system. First, we present the reduction method based on a complex admittance matrix [Y(s)] of the whole initial model. From which we obtain by two inversions, the matrix $[Y_{\rm red}(s)]$, which can be interpreted as a reduced network. We give an example of application of the numeric reduction method. The same method is applied with success to analytical expression of impedances kept from the quadrupole representation of heat conduction. In order to simulate easily the transient responses of analytical models, we present the development of analytical impedance in the form of an equivalent network, which is proved to be very efficient during simulations. The first application is done with a heterogeneous system made of two bars of different materials, one is made of copper and the other is made of steel. The second application is done with a more complex thermal system constituting a cooler with 7 branches. This cooler is reduced to 1, 2 and 3 nodes to obtain the simplest model while reflecting as far as possible the dynamic behaviour. This document presents a generalisation of the method of network reduction in the case where the models' impedances have analytical expressions. In this case, we show that contrary to the numerical reduction, which approximates admittances to the first order, we are free to choose the model order, whatever the kept nodes, in such a manner that the model's bandwidth is considered as sufficient. The resulting equivalent networks allow easy simulations of the transient responses thanks to standard electric network softwares. Beyond the dealt examples of analytical reduction, for industrial systems non analytically calculable but governed by an equation of heat diffusion, the structures (topologies) of the reduced models would be the same. That opens prospects to obtain thermal reduced models from an automated networking realised in CAD.

An analytical method is proposed to calculate the free surface deformation induced by an inclusion embedded in a thin slab. The displacement of the free surface has been determined with the help of the 2D Fourier transformation, as well as the momenta of the displacements when they exist. Comparing the deformations induced by the same inclusion in a semi-infinite medium and in a slab, it has been demonstrated that the deformations in the slab are much more localized than in a semi-infinite solid. A simple example is finally given concerning a latent track induced by swift heavy ion going through a solid.

Femtosecond modelocked lasers using new ytterbium-doped borate crystals (Yb:Sr3Y(BO3)3, Yb:Ca4GdO(BO3)3 and Yb:Ca4YO(BO3)3) are demonstrated. Pulse duration as short as 69 fs has been obtained. To modelock such lasers, fast saturable absorbers need to be used. Two different types of fast saturable absorbers have been studied: low-temperature-grown semiconductor mirrors (SESAM) and high-energy-ion-implanted semiconductor Bragg reflectors (SBR). We demonstrated, for the first time to our knowledge, that ion-implanted SBR can be used to modelock oscillators using Yb-doped materials.

Bimetallic particles (10–20 nm), with a Cu or Ag core and a Pd shell were elaborated by sequential impregnations on various oxides. Their shapes are limited by (100) and (111) faces which correspond to the planes of lowest surface energy for pure fcc metal particles of the same size. The Pd shells are epitaxially oriented on the core and locally accommodated to the metal lattice. In the case of Pd/Cu particles, annealing at 400 °C induces the structural transition to the ordered structure with shapes limited by (111), (001) and (110) faces. The adhesion energy of the annealed particles does not seem to depend on the substrate.

We describe the Teramobile system, a new mobile femtosecond multi-terawatt laser and detection system based on a state-of-the art CPA laser system embedded in a standard freight container, as well as a mobile detection unit allowing a characterization of the nonlinear propagation of high power laser pulses over long horizontal distances. The unique mobility feature of the whole system opens the way to previously unreachable applications for high-power laser pulses in the field of atmospheric research (lidar, laser-triggered lightning), which are also briefly reviewed.

This work presents the thermal field computation of a wire getting a laser supported material cladding. We present two complementary models, based on finite volume approaches. First, we present a one dimensional model in which moving of the wire is integrated by mean of an advection term in the heat diffusion equation. It gives the mean temperature variation along the wire An analytical solution of this problem is also given. Secondly, a three-dimensional model gives the complete thermal field. These two models are confronted with experiments. The result of the first one is compared to a maximum mean temperature measuring. The second is validated by comparison with microphotography of the melted zone, and in-section micro-hardness measurements.

The properties of Cr3+ in LiNbO3 single crystals have been investigated by means of several experiments including the recordings of absorption and high resolution laser spectroscopy spectra with dye-laser excitation spectra, emission spectra and fluorescence decays under laser selective pumping. Measurements performed on crystals with composition varying between congruent and close to stoichiometry enabled new features to be revealed which lead us to re-interpret the optical spectra of chromium-doped LN. Three chromium centres are sufficient to explain the main optical features. The main chromium centre labelled γ, giving rise to the broad absorption and emission bands, corresponds to the low-crystal field scheme where the 4T2 level is lower than 2E. The two other chromium centres α and β yield sharp lines in emission and correspond to the high-crystal field scheme. Their dependencies on both the chromium concentration and the composition were studied using emission spectroscopy at low temperature. The main centre γ seems slightly affected by chromium concentration or composition change. The centres α and β are shown to be strongly connected to the presence in their surrounding of intrinsic defects related to the crystal non-stoichiometry. From their behaviour versus Cr concentration, the origin of these centres is discussed in terms of perturbed substitution.

Commercial grating-tuned single-mode extended-cavity semiconductor lasers (ECLD's) can be tuned over 100 nm around 1.55 μm. This continuous tuning with no mode-hopping requires delicate factory adjustments and a high mechanical stability. These constrains are relaxed by the adjunction of a photorefractive crystal inside the cavity which creates an adaptive spectral filter which decreases the loss of the lasing-mode and thus enhances its stability.

A closed form solution of the general case of frequency shift of a Gaussian pulse in a nonlinear power law attenuating medium of arbitrary exponent including the effect of transient radiation coupling process is presented. Also, this paper describes a simulation of the spectrum pathway in an ultrasonic A-scan. It includes transducer response, frequency dependent absorption in the test medium and radiation coupling transfer function. The measurement and simulation result has been used with the closed form solution to correct the absorption filter (attenuation coefficient). The attenuation coefficient correction for castor oil to fit the simulation result with recorded data is examined.

The scanning electron microscope mirror (SEMM) method is considered as a suitable approach for the characterisation of the charge trapping ability of insulators. However, the interpretation of the experimental results is far from being obvious. The aim of this paper is to give some new insights in this problem. Our description of the mirror plots is conventionally based on a multipole analysis of the charge distribution and on the radius of curvature approximation. This approach indicates that the trend of the plots is mainly controlled by the quadrupole contribution. This clearly illustrates the non- uniqueness of the interpretation since different trapped charge distributions, but with nearly equal quadrupole terms, can produce rather similar mirror plots. To make the problem unambiguous, a semi-ellipsoidal shell model is used to account for the implanted space charge. Within this model, we propose a simple method to get the mean density of trapped charge ρ0. Our Monte Carlo simulations of the charge implantation phase show that ρ0 can strongly differ from the density of traps NT. The reasons for these deviations are discussed for a significant set of values of NT and of the primary energy Ep.

In this article we report a new wavefront sensor, developed at the Laboratoire de Spectroscopie Atomique et Ionique, for a full characterization of soft X-ray beams. The Shack-Hartmann sensor has a theoretical accuracy in the order of $\lambda/100$ at a wavelength around 13 nm. A cartography of the wave-vectors pointing of laser-pumped soft X-ray laser has been achieved. It has shown the presence of many ripples probably coming from plasma instabilities. Capillary discharge soft X-ray laser has been also investigated. For all the pumping configurations, the wavefront is spherical, divergent with a radius of about 6.5 m at 2.5 m from the plasma end. The best wavefront exhibits an error to a perfect wave of 3λ rms. Assuming to focus the beam with a f = 50 mm diffraction-limited mirror, a theoretical focal spot size of 0.5 μm in diameter have been estimated containing 70% of the incident energy. In that case an intensity of 4 × 1013 W cm−2 should be achieved.

The presented study concerns the dynamics of the arc in a low-voltage breaking device. For this study, two methods of diagnostics are used: a magnetic diagnostics based on punctual measurements of the induction and an optical diagnostics using a high-speed camera and a CCD camera. These two diagnostics are compared for different experimental conditions.

We have implemented a real-time numerical denoising algorithm, using the Discrete Wavelet Transform (DWT), on a TMS320C3x Digital Signal Processor (DSP). We also compared from a theoretical and practical viewpoints this post-processing approach to a more classical low-pass filter. This comparison was carried out using an ECG-type signal (ElectroCardiogram). The denoising approach is an elegant and extremely fast alternative to the classical linear filters class. It is particularly adapted to non-stationary signals such as those encountered in biological applications. The denoising allows to substantially improve detection of such signals over Fourier-based techniques. This processing step is a vital element in our acquisition chain using high sensitivity magnetic sensors. It should enhance detection of cardiac-type magnetic signals or magnetic particles in movement.