Mid-infrared Vertical cavity surface emitting lasers (MIR-VCSEL) are very attractive compact sources for spectroscopic measurements above 2μm, relevant for molecules sensing in various application domains. A long-standing issue for long wavelength VCSEL is the large structure thickness affecting the laser properties, added for the MIR to the tricky technological implementation of the antimonide alloys system. In this paper, we propose a new geometry for MIR-VCSEL including both a lateral confinement by an oxide aperture, and a high-contrast sub-wavelength grating mirror (HCG mirror) formed by the high contrast combination AIOx/GaAs in place of GaSb/A│AsSb top Bragg reflector. In addition to drastically simplifying the vertical stack, HCG mirror allows to control through its design the beam properties. The robust design of the HCG has been ensured by an original method of optimization based on particle swarm optimization algorithm combined with an anti-optimization one, thus allowing large error tolerance for the nano-fabrication. Oxide-based electro-optical confinement has been adapted to mid-infrared lasers, byusing a metamorphic approach with (Al) GaAs layer directly epitaxially grown on the GaSb-based VCSEL bottom structure. This approach combines the advantages of the will-controlled oxidation of AlAs layer and the efficient gain media of Sb-based for mid-infrared emission. We finally present the results obtained on electrically pumped mid-IR-VCSELs structures, for which we included oxide aperturing for lateral confinement and HCG as high reflectivity output mirrors, both based on AlxOy/GaAs heterostructures.

Indium Phosphide is a material of primary relevance in the field of opto-electronics since it supersedes conventional materials such as AsGa for electron mobility and heat conduction for instance. It is often doped with iron to reduce its conductivity and enhance its light dependent conduction properties.Indium Phosphide is well known for its two carrier band transport conduction mechanism, where both electrons and holes play a significant role. Its transport mechanisms have been heavily investigated, especially in the dark. Light induced charge transport, on the contrary, has beeninvestigated at the end of the XX th century as far as periodic illumination stemming from beam interference is concerned. More recently, non periodic illumination was tackled. Both have shown the existence of a particular intensity, named the resonance intensity, at which charge transportis enhanced and around which it changes behavior. Both have in common the small modulation hypothesis where ligh intensity is assumed not to deviate too far from its mean value. InP:Fe being a electro-optic material, this resonance mechanism has been shown to be at the heartof a light induced refractive index modulation, leading to light self-focusing. However, a one beam illumination is far from the small modulation hypothesis. Experiments indeed show that the very notion of resonance intensity no longer holds. They also show a behavior-reversal intensity. Itsvalue is different from that of the resonance intensity, but remains to be explained. We attempt here a theoretical study of the two carrier band transport model in InP:Fe, in the simplifying framework of one single space dimension alongside the time dimension. Our originalapproach is to rule out all conventional approximations, aiming to justify each of them mathematically with precise numerical values. Once this is done, we go on to a simplified model of two carrier transport in InP:Fe, for which basic simulation will be undertook and checked against experimentalresults. The mathematical method undertook here is know as multi-scale modeling. It is needed because of the presence of largely varying orders of magnitudes in the parameters of the two carrier band transport model.

A new architecture for mid-infrared (MIR) Vertical Cavity Surface Emitting Laser (VCSEL) is proposed and fabricated. The MIR-VCSEL structure includes both a lateral confinement by an oxide aperture, and a high-contrast sub-wavelength grating mirror (HCG mirror) formed by the high contrast combination AlOx/GaAs, and that replaces conventional GaSb/AlAsSb top Bragg mirror. Upon the GaSb-based half-microcavity bottom part, a metamorphic AlGaAs heterostructure was epitaxially grown to enable thermal oxidation and grating mirror fabrication steps on AlGaAs material platform. The optical design of the VCSEL structure and more precisely the HCG mirror has been optimized thanks to an original methodology based on optimization and anti-optimization methods, resulting in improved parameter tolerances regarding processing errors. After all, we show the complete fabrication of an electrically-pumped MIR monolithic VCSEL structure by integrating this new technological bricks.

The design and optimization of novel structures is an essential part of the next-generation solar cells development. Indeed, the technological steps involved in the development of high-performance solar cells involve a huge set of interdependent physical and geometrical parameters: layers thicknesses, dopings, compositions, and defect characteristics. In this work, we propose a new open-source and free solar cell optimizer: SLALOM À for SoLAr ceLl multivariate OptiMizer À that implements a rigorous multivariate approach, which improves from the one-parameter-at-a-time procedure that is traditionally used in the field to a state-of-the-art multivariate approach. Applied to indium gallium nitride (InGaN) solar cells, it shows its potential to become a useful tool for the development of novel solar cells. SLALOM is implemented to be extended to any semiconductor simulation engine. Several models for solar cells have been implemented in SLALOM, including, for instance, InGaN. One can adapt these models to any solar cell technology by changing the parameter set, the here proposed generic code structure remaining unchanged.

This work is devoted to the design of high contrast grating mirrors taking into account the technological constraints and tolerance of fabrication. First, a global optimization algorithm has been combined to a numerical analysis of grating structures (RCWA) to automatically design HCG mirrors. Then, the tolerances of the grating dimensions have been precisely studied to develop a robust optimization algorithm with which high contrast gratings, exhibiting not only a high efficiency but also large tolerance values, could be designed. Finally, several structures integrating previously designed HCGs has been simulated to validate and illustrate the interest of such gratings.

Le point de vue d'un enseignant-chercheur sur le mouvement de la Science Ouverte

If there is a suspicion of a systemic autoimmune disease, a two-step assessment of autoantibodies (AAb) is recommended for the serological diagnosis thereof. First, AAb will be determined using sensitive, cell-based indirect immunofluorescence. Then, a positive result must be confirmed with a more specific test due to the possibility of false-positive results. This gradual approach is necessary because there is currently no assay technique that fulfills the requirements for a one-stage procedure for sensitivity and specificity. For effective AAb analysis, simultaneous determination of several AAb with multiparametric confirmatory assays significantly shortens serological diagnosis, compared with conventional monoparametric testing. Yet, currently available multiparametric AAb detection techniques do not offer the combination of screening and confirmatory testing. Thus, a new approach based on digital fluorescence was developed by applying a novel CytoBead technology that is presented here. The aim was to combine the recommended stepwise approach consisting of sensitive screening and confirmation of specific diagnosis in a reaction environment and thereafter the possibility of adaptation to the serological diagnosis of several autoimmune diseases. Using standard microscopic glass slides and the combination of native cellular or tissue substrates with autoantigen-loaded fluorescent microparticles (beads) in a reaction environment, along with the possibility of manual and automatic evaluation by IIF and the quantitative measurement of fluorescent signals, the disadvantages of currently existing test systems could be overcome. This novel concept is applicable for the determination of various multiparametric AAb, e.g., the determination of antinuclear antibodies and the corresponding AAb in molecular cytoplasmic and nuclear autoantigenic structures. Further, this becomes the basis for the simultaneous multiparametric AAb determination for the serology of celiac disease or ANCA-associated vasculitides.

The analysis of different biomolecules is of prime importance for life science research and medical diagnostics. Due to the discovery of new molecules and new emerging bioanalytical problems, there is an ongoing demand for a technology platform that provides a broad range of assays with a user-friendly flexibility and rapid adaptability to new applications. Here we describe a highly versatile microscopy platform, VideoScan, for the rapid and simultaneous analysis of various assay formats based on fluorescence microscopic detection. The technological design is equally suitable for assays in solution, microbead-based assays and cell pattern recognition. The multiplex real-time capability for tracking of changes under dynamic heating conditions makes it a useful tool for PCR applications and nucleic acid hybridization, enabling kinetic data acquisition impossible to obtain by other technologies using endpoint detection. The paper discusses the technological principle of the platform regarding data acquisition and processing. Microbead-based and solution applications for the detection of diverse biomolecules, including antigens, antibodies, peptides, oligonucleotides and amplicons in small reaction volumes, are presented together with a high-content detection of autoimmune antibodies using a HEp-2 cell assay. Its adaptiveness and versatility gives VideoScan a competitive edge over other bioanalytical technologies.