Electromagnetic theory is used to calculate the gradual loss of polarization in light scattering from surface roughness. The receiver aperture is taken into account by means of a multiscale spatial averaging process. The polarization degrees are connected with the structural parameters of surfaces.

The polarization of a coherent depolarized incident light beam passing through a scattering medium is investigated at the speckle scale. The polarization of the scattered far field at each direction and the probability density function of the degree of polarization are calculated and show an excellent agreement with experimental data. It is demonstrated that complex media may confer high degree of local polarization (0.75 DOP average) to the incident unpolarized light.

A laser damage test facility delivering pulses from 100 fs to 3 ps and designed to operate at 1030 nm is presented. The different details of its implementation and performances are given. The originality of this system relies the online damage detection system based on Nomarski microscopy and the use of a non-conventional energy detection method based on the utilization of a cooled CCD that offers the possibility to obtain the laser induced damage threshold (LIDT) with high accuracy. Applications of this instrument to study thin films under laser irradiation are presented. Particularly the deterministic behavior of the sub-picosecond damage is investigated in the case of fused silica and oxide films. It is demonstrated that the transition of 0-1 damage probability is very sharp and the LIDT is perfectly deterministic at few hundreds of femtoseconds. The damage process in dielectric materials being the results of electronic processes, specific information such as the material bandgap is needed for the interpretation of results and applications of scaling laws. A review of the different approaches for the estimation of the absorption gap of optical dielectric coatings is conducted and the results given by the different methods are compared and discussed. The LIDT and gap of several oxide materials are then measured with the presented instrument: Al(2)O(3), Nb(2)O(5), HfO(2), SiO(2), Ta(2)O(5), and ZrO(2). The obtained relation between the LIDT and gap at 1030 nm confirms the linear evolution of the threshold with the bandgap that exists at 800 nm, and our work expands the number of tested materials.

A single procedure based on speckle statistics is proposed to identify the scattering origins of light (surface or bulk). Successful results are obtained with high-scattering samples, which offers complementary techniques for imaging or characterization in random media. The speckle statistics are shown to be correlated to partial polarization. Angle-resolved ellipsometric data confirm all conclusions.

ZrO2-SiO2 and Nb2O5-SiO2 mixture coatings as well as those of pure zirconia (ZrO2), niobia (Nb2O5), and silica (SiO2) deposited by ion-beam sputtering were investigated. Refractive-index dispersions, bandgaps, and volumetric fractions of materials in mixed coatings were analyzed from spectrophotometric data. Optical scattering, surface roughness, nanostructure, and optical resistance were also studied. Zirconia-silica mixtures experience the transition from crystalline to amorphous phase by increasing the content of SiO2. This also results in reduced surface roughness. All niobia and silica coatings and their mixtures were amorphous. The obtained laser-induced damage thresholds in the subpicosecond range also correlates with respect to the silica content in both zirconia- and niobia-silica mixtures.

International audienceIn photonics, the field concentration and enhancement have been major objectives for achieving sizereduction and device integration. Plasmonics offers resonant field confinement and enhancement, butultra-sharp optical resonances in all-dielectric multi-layer thin films are emerging as a powerful contestant.Thus, applications capitalizing upon stronger and sharper optical resonances and larger fieldenhancements could be faced with a choice for the superior platform. Here, we present a comparisonbetween plasmonic and dielectric multi-layer thin films for their resonance merits. We show that theremarkable characteristics of the resonance behavior of optimized dielectric multi-layers can outweighthose of their metallic counterpart

This new microscopy technique achieves unprecedented contrast for the study of nanomaterials and their chemical modification.

International audienceWe review recent advances in the control of diffusion processes in thermodynamicsand life sciences through geometric transforms in the Fourier and Fick equations,which govern heat and mass diffusion, respectively. We propose to further encom-pass transport properties in the transformed equations, whereby the temperatureis governed by a three-dimensional, time-dependent, anisotropic heterogeneousconvection-diffusion equation, which is a parabolic partial differential equationcombining the diffusion equation and the advection equation. We perform twodimensional finite element computations for cloaks, concentrators and rotators ofa complex shape in the transient regime. We precise that in contrast to invisibilitycloaks for waves, the temperature (or mass concentration) inside a diffusion cloakcrucially depends upon time, its distance from the source, and the diffusivity ofthe invisibility region. However, heat (or mass) diffusion outside cloaks, concen-trators and rotators is unaffected by their presence, whatever their shape or posi-tion. Finally, we propose simplified designs of layered cylindrical and sphericaldiffusion cloaks that might foster experimental efforts in thermal and biochem-ical metamaterials