THALES long wave QWIP thermal imagers

THALES have developed for volume manufacture high performance low cost thermal imaging cameras based on the THALES Research Technology (TRT) third generation gallium arsenide long wave QWIP array. Catherine XP provides 768 × 575 CCIR video resolution and Catherine MP provides 1280 × 1024 SXGA video resolution. These compact and rugged cameras provide 24 h passive observation, detection, recognition, identification (DRI) in the 8–12 μm range, providing resistance to battlefield obscurants and solar dazzle, and are fully self contained with standard power and communication interfaces. The cameras have expansion capabilities to extend functionality (for example, automatic target detection) and have network battlefield capability. Both cameras benefit from the high quantum efficiency and freedom from low frequency noise of the TRT QWIP, allowing operation at 75 K, low integration times and non interruptive non uniformity correction. The cameras have successfully reached technology readiness level 6/7 and have commenced environmental qualification testing in order to complete the development programmes. These latest additions to the THALES Catherine family provide high performance thermal imaging at an affordable cost.     

Modelling of long term kinetic evolution: a fruitful relationship between experiment and theoretical development

Recent developments in multi-scale modelling, based on atomic scale calculations, are leading to a growing conviction that modelling will soon be used to design material components for nuclear reactors. In this article we discuss this assumption on the basis of the relationship between experimental studies and theoretical calculations of the microstructural evolution of materials under irradiation. In the first part of the paper, the available numerical models for long term microstructural evolutions are briefly reviewed. The experimental methods are presented in a second part. In the third part, several examples of fruitful relationships between modelling and experiments are discussed. To cite this article: A. Barbu, C. R. Physique 9 (2008).     

La détection infrarouge avec les plans focaux non refroidis : état de l'artUncooled focal plane infrared detectors: the state of the art

The emergence of uncooled detectors has opened new opportunities for IR detection for both military and commercial applications. Development of such devices involves a lot of trade-offs between the different parameters that define the technological stack. These trade-offs explain the number of different architectures that are under worldwide development. The key factor is to find a high sensitivity and low noise thermometer material compatible with silicon technology in order to achieve high thermal isolation in the smallest area as possible. Ferroelectric thermometer based hybrid technology and electrical resistive thermometer based (microbolometer) technology are under development. LETI and ULIS have chosen from the very beginning to develop first a monolithic microbolometer technology fully compatible with commercially available CMOS technology and secondly amorphous silicon based thermometer. This silicon approach has the greatest potential for reducing infrared detector manufacturing cost. After the development of the technology, the transfer to industrial facilities has been performed in a short period of time and the production is now ramping up with ULIS team in new facilities. LETI and ULIS are now working to facilitate the IRFPA integration into equipment in order to address a very large market. Achievement of this goal needs the development of smart sensors with on-chip advanced functions and the decrease of manufacturing cost of IRFPA by decreasing the pixel pitch and simplifying the vacuum package. We present in this paper the technology developed by CEA/LETI and its improvement for being able to designs 384×288 and 160×120 arrays with a pitch of 35 μm. Thermographic application needs high stability infrared detector with a precise determination of the amount of absorbed infrared flux. Hence, infrared detector with internal temperature stabilized shield has been developed and characterized. These results will be presented. To cite this article: J.-L. Tissot, C. R. Physique 4 (2003).     

Les nouvelles générations de détecteurs infrarouge à base de HgCdTeNew generations of infrared detectors based on HgCdTe

The technology of very high performance cooled infrared detectors made with HgCdTe has progressed continuously for ten years and reached today an industrial maturity that allows the production of large size arrays at a more and more reasonable cost. At the same time, new prototypes of more complex sensors have appeared (megapixel arrays, multicolour arrays, high definition long linear arrays, …) that show the strong potentialities of this very high performance technology. This paper presents the technology developed in France and gives the state of the art of products available in industry; it then focuses on some very recent realizations of advanced prototypes made at LETI (dualband arrays, megapixel arrays, …). To cite this article: G. Destefanis, C. R. Physique 4 (2003).     

Caractérisation et modélisation de composants matriciels infrarougeCharacterization and modelling of IR sensors

The objective of this paper is to describe the first behavioural models of cooled (based on HgCdTe photodetectors) infrared sensors which were designed at CEA-LETI/SLIR. In this way, the interest of such an approach in the evaluation and improvement of optronic systems will be shown. The paper first presents the modelling approach (architecture of the models, choice of parameters, tools for modelling and calibration, …). Then models are compared to measurements on real components in order to verify the efficiency of the modelling approach. To cite this article: P. Castelein, C. R. Physique 4 (2003).     

Time-reversed waves and super-resolution

Time-reversal mirrors (TRMs) refocus an incident wavefield to the position of the original source regardless of the complexity of the propagation medium. TRMs have now been implemented in a variety of physical scenarios from GHz microwaves to MHz ultrasonics and to hundreds of Hz in ocean acoustics. Common to this broad range of scales is a remarkable robustness exemplified by observations at all scales that the more complex the medium (random or chaotic), the sharper the focus. A TRM acts as an antenna that uses complex environments to appear wider than it is, resulting for a broadband pulse, in a refocusing quality that does not depend on the TRM aperture.Moreover, when the complex environment is located in the near field of the source, time-reversal focusing opens completely new approaches to super-resolution. We will show that, for a broadband source located inside a random metamaterial, a TRM located in the far field radiated a time-reversed wave that interacts with the random medium to regenerate not only the propagating but also the evanescent waves required to refocus below the diffraction limit. This focusing process is very different from that developed with superlenses made of negative index material only valid for narrowband signals. We will emphasize the role of the frequency diversity in time-reversal focusing. To cite this article: M. Fink et al., C. R. Physique 10 (2009).     

New techniques of characterisation

During the last decade, amazing advances in microelectronics have led to the development of large infrared focal plane arrays (IRFPAs) with a high density of pixels per square centimetre. Bispectral and soon multispectral detectors are now under development. In order to follow or even anticipate this race for spatial and spectral resolution, new techniques of characterisation have been developed in our laboratory, allowing the measurement of the spatial and spectral responses of a hundred of thousands pixels forming the IRFPA. Thus, a test bench for the measurement of hyperspectral cartographies has been realised. The principle of measurement and experimental results will be presented. For the measurement of spatial responses, the projection of targets that illuminate the entire surface of the IRFPA and contain sub-pixel details is required in order to extract the line (or spot) spread function of every pixel. For this, non-imaging techniques of projection based on the self-imaging property of periodic targets have been elaborated. The first results and the potential of this original approach will be discussed. To cite this article: N. Guérineau et al., C. R. Physique 4 (2003).     

Helium and point defect accumulation: (i) microstructure and mechanical behaviour

Ferritic/martensitic (F/M) steels are good candidate structural materials for the future fusion reactors and spallation sources. However, irradiation of steels is known to produce hardening, loss of ductility, shift in ductile to brittle transition temperature (DBTT) and reduction of fracture toughness and creep resistance starting at low doses. Helium (He), produced by transmutation during the irradiation, also impacts mechanical properties. Numerous experimental and theoretical studies on the evolution of the microstructure of steels under irradiation have been conducted until now. We review the effect of irradiation-induced point defects and in particular of He on the mechanical properties of F/M steels. To cite this article: R. Schäublin et al., C. R. Physique 9 (2008).     

Metamaterials and invisibility

Metamaterials have significantly extended the range of electromagnetic properties available to device designers. An interesting application of these new materials is to the problem of cloaking, where the goal is to render an object invisible to electromagnetic radiation within a certain frequency range. Here, I review the concepts behind recently-proposed invisibility cloaks, and the way in which metamaterials can allow these designs to be realized. To cite this article: B. Wood, C. R. Physique 10 (2009).     

On practical aspects of Laser Guide Stars

The Gemini Observatory has developed an extensive Adaptive Optics (AO) program, including Classical AO, Laser Guide Star (LGS) AO, Multi-Conjugate AO (MCAO), extreme AO (eXAO) and Ground Layer AO (GLAO). Most of these instruments use one or several LGSs. A laser has been in operation at Gemini since May 2005. Most of the laser related systems (beam transport, launch, safety systems) have been developed in house. These are major components, requiring a development effort not to be underestimated. In this article, we propose to share the Gemini experience in terms of practical issues and calibration requirements associated with the use of lasers in AO. To cite this article: F. Rigaut, C. d'Orgeville, C. R. Physique 6 (2005).     

Resonant Inelastic X-ray Scattering: From band mapping to inter-orbital excitations

Resonant inelastic X-ray scattering (also known as resonant X-ray Raman spectroscopy when only valence and conduction states are involved in the final state excitation) has developed into a major tool for understanding the electronic properties of complex materials. Presently it provides access to electron excitations in the few hundred meV range with element and bulk selectivity. Recent progress in X-ray optics and synchrotron radiation engineering have opened up new perspectives for this powerful technique to improve resolving power and efficiency. We briefly present the basics of the method and illustrate its potential with examples chosen from the literature. To cite this article: J. Lüning, C.F. Hague, C. R. Physique 9 (2008).     

Cloaking by plasmonic resonance among systems of particles: cooperation or combat?

We study quasistatic cloaking by the mechanism of plasmonic resonance, for systems of coated cylinders. Our focus is on the nature of the resonant cloaking interaction: whether systems of particles can be made to cooperate in cloaking a polarizable particle from an applied uniform field. We show that in fact if the cloaking regions of the systems of particles overlap, then they tend to interact in a fashion detrimental to their cloaking of the polarizable particle. If the cloaking regions touch but do not overlap, then the system of particles can cloak a larger region than each would in isolation. To cite this article: R.C. McPhedran et al., C. R. Physique 10 (2009).     

Exploring the electronic band structure of individual carbon nanotubes under 60 T

Nano-sciences, and in particular nano-physics, constitute a fascinating world of investigations where the experimental challenges are to synthesize, to address (for instance optically or electrically) to explore and promote the remarkable physical properties of new nano-materials. Somehow, one of the most promising realization of nano-sciences lies in carbon-based nano-materials with sp² covalent bonds. In particular, carbon nanotubes, graphene and more recently ultra-narrow graphene nano-ribbons are envisioned as elementary bricks of the future of nano-electronics. However, prior to such an achievement, the first steps consist in understanding their fundamental electronic properties when they constitute the drain–source channel of a gated device or inter-connexion elements. In this article, we present the richness of challenging experiments combining single-object measurements with an extreme magnetic environment. We demonstrate that an applied magnetic field (B), along with a control of the electrostatic doping, drastically modifies the electronic band structure of a carbon nanotube based transistor. Several examples will be addressed in this presentation. When B is applied parallel to the tube axis, a quantum flux threading the tube induces a giant Aharonov–Bohm conductance modulation mediated by Schottky barriers whose profile is magnetic field dependent. In the perpendicular configuration, the applied magnetic field breaks the revolution symmetry along the circumference and non-conventional Landau states develop in the high field regime. By playing with a carbon nanotube based electronic Fabry–Perot resonator, the field dependence of the resonant states of the cavity reveals the onset of the first Landau state at zero energy. These experiments enlighten the outstanding efficiency of magneto-conductance experiments to probe the electronic properties of carbon based nano-materials. To cite this article: S. Nanot et al., C. R. Physique 10 (2009).     

Role of patterning in islands nucleation on semiconductor surfaces

Quantum dots (QDs) grown on semiconductors surfaces are actually the main researchers' interest for applications in the forthcoming nanotechnology era. New frontiers in nanodevice technology rely on the precise positioning of the nucleation site and on controlling the shape and size of the dots. In this article we will review some recent studies regarding the control of the nucleation process on semiconductor surfaces. A few approaches to form ordered patterns on surfaces are described: natural patterning induced by surface instabilities (as step bunching or step meandering), in situ substrate patterning by Scanning Tunneling Microscopy (STM), high resolution patterning by Focused Ion Beam (FIB). Growth of epitaxial layers of semiconductors (Ge/Si(100) and InAs/GaAs(100)) on patterned surfaces has been studied by STM or Atomic Force Microscopy (AFM) unveiling the way in which the first atoms start to aggregate and identifying their exact nucleation site. Control of the dot size to match the patterning typical wavelength has been achieved by using surfactants on misoriented substrates. STM images acquired in real time allows one to identify the mechanism of Ge cluster formation on patterned Si(100), and to follow the island transition from pre-pyramid to pyramid. Nucleation of ordered Ge dots on SiO₂ substrates has been obtained thanks to FIB tight patterning, achieving island densities of 3.5×10¹⁰/cm². To cite this article: N. Motta et al., C. R. Physique 7 (2006).     

A lightning initiation mechanism: application to a thunderstorm electrification model

The use of numerical models has greatly increased our understanding of the electrical and microphysical process within electrified clouds. We use the University of Washington, 1.5-dimensional thunderstorm model to examine the effects of including a runaway electron based lightning initiation mechanism. We find that this mechanism can significantly alter the electrification history of modeled storms and produce vertical electric field profiles that are very similar to those of observed storms. To cite this article: R. Solomon et al., C. R. Physique 3 (2002) 1325–1333.     

Phase-shift, refraction and focusing based on the metamaterial technologies

We address the problem of positive phase-shifting, negative refraction and focusing via a flat lens on the basis of the metamaterial technologies. With this aim, three examples are considered which differ by the technology employed and the operating frequency. The first one concerns negative-zero-positive refraction by using a prism-shaped electromagnetic metamaterial which consists of omega-type inclusion arrays operating at microwaves. The experimental verification was done in this case by angle-resolved transmission measurements. Second, we report on the phase-shift properties of a negative index transmission line which operates at Terahertz frequencies. In order to experimentally demonstrate the left-handed character of the propagation along the line, resulting in a phase advance, we used time domain experiments. At last, focusing by double refraction in a flat negative index lens was demonstrated by the theoretical and experimental mapping of the intensity of the electric field. Such a mapping of the E-field was carried out at near infrared (1.5 μm) by analysis in the time domain and scanning by near field optical microscopy. To cite this article: D. Lippens, C. R. Physique 10 (2009).     

Helium and point defect accumulation: (ii) kinetic modelling

The main outstanding issues regarding modeling He diffusion and defect accumulation in α-iron are reviewed. During recent years, first principles calculations have provided a better understanding of defect stability and migration properties in pure α-iron, and accurate values of energetics of He migration and He-vacancy interactions. Such information has been used by several authors to study damage evolution under different irradiation conditions using both kinetic Monte Carlo and rate theory models. In this article a review of the main results is provided, in particular for He desorption. The influence of impurities such as carbon is discussed as well as the main challenges ahead for modeling. To cite this article: M.J. Caturla et al., C. R. Physique 9 (2008).     

Multi-Conjugate Adaptive Optics for ELTs: constraints and limitations

We present how enlarging the size of a telescope from the current 10 meter telescope to the future 100 meter Extremely Large Telescopes increases the complexity of a classical or multiconjugate adaptive optics instrument. We point out elements or parameters of the system for which it is critical to propose new ideas as solutions and we study the effect of the increase of the diameter on the point spread function of an MCAO and a Ground Layer AO system. To cite this article: R. Ragazzoni et al., C. R. Physique 6 (2005).