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Le projet ALOHA propose une nouvelle génération d’instruments dédiés à l’imagerie haute résolution en astronomie. Celui-ci a pour objectif de relier un réseau de télescopes hectométrique par fibre optique en utilisant conjointement la somme de fréquence pour adapter le rayonnement astronomique à un dispositif optimisé avec des composants fibrés ou guidés issus de la bande télécom. Ce travail a été effectué au laboratoire XLIM et sur ciel à l’observatoire du Mount Wilson (CA USA).

In the framework of the ALOHA (Astronomical Light Optical Hybrid Analysis) project, dedicated to high resolution imaging in the L-band using optical fibre and nonlinear optics, we have implemented a servo controlled hectometric outdoor fibre link between two telescopes and the recombination beam facility of the CHARA telescope array. A two-stage servo system using optical fibre modulator, fibre delay line, and a metrology laser at 1064 nm allows to stabilise the optical path difference within 3 nm RMS over a 3000 s record. Using an internal source at 810 nm, the signal-to-noise ratio of the fringe modulation peak is enhanced by a factor better than two when the servo control is switched on. This study can be also considered as a seminal work towards very long base fibre linked telescope arrays and allows to scale the perturbative environment of an outdoor fibre link.

In the framework of the Astronomical Light Optical Hybrid Analysis (ALOHA) laboratory mid-infrared (MIR) up-conversion fibred interferometer in the L band, we report on the influence of the input-stage architecture. Using an amplitude division set-up in the visible or near-infrared is a straightforward choice in most cases. In the MIR context, the results are slightly different and we show that a wavefront division set-up is needed. These in-laboratory principle experiments allow us to measure a reliable 88 per cent instrumental contrast with high flux and to obtain fringes from faint sources at 3.5 μm with a spectral bandwith of 37 nm converted to 817 nm. An equivalent limiting L-band magnitude around 3.9, equivalent to 3.0 fW nm−1, could be demonstrated on 1 m class telescopes. This opens the possibility of planning future on-sky tests at the Center for High Angular Resolution Astronomy (CHARA) array and of predicting the performance attained.

Les moyens d’observation en astronomie n’ont cessé d’évoluer au fil des siècles. L’utilisation de réseaux de télescopes permet aujourd’hui d’avoir des détails de plus en plus fins dans les images obtenues (grande résolution). Dans ce contexte, le projet ALOHA propose une approche totalement originale consistant à changer la couleur de la lumière de l’objet observé au niveau de chaque télescope du réseau avant de la détecter. Cela permet d’éviter d’utiliser des systèmes de cryogénie très coûteux et complexes nécessaires lors de la collecte de lumière moyen et lointain infrarouge. Ce document présente quelques éléments sur nos activités de recherche sur le projet ALOHA.

Multimode optical fibers (MMFs) are an excellent alternative to single-mode fibers for applications where high power level is required or for investigating spatiotemporal nonlinear wave propagation [1] . Recent experiments have shown that it is possible to achieve a speckleless output beam in MMF through a novel nonlinear effect called Kerr-induced beam self-cleaning (KBSC) [2] . This effect has been observed in a wide variety of MMFs, including standard graded-index (GRIN) MMFs and photonic crystal fibers (PCFs). Here, we report on the observation of low-peak-power KBSC and supercontinuum generation (SCG) in a few-mode PCF with a GRIN core.

En 2014, 69 600 personnes de 50 ans ou plus dont 15 200 de 60 ans ou plus sont accueillies dans un etablissement pour adultes handicapes. De plus, 18 400 personnes handicapees de 50 ans ou plus dont 4 900 de 60 ans ou plus sont accompagnees a domicile par un service dedie. Entre 2010 et 2014, la croissance du nombre de personnes au-dela de ces seuils d’âge est plus elevee dans les etablissements et services d’accompagnement pour adultes handicapes que dans l’ensemble de la population francaise. La part des etablissements qui accueillent des personnes handicapees vieillissantes a augmente de 39,9 % a 58,8 % en quatre ans. Les personnes handicapees de 60 ans ou plus, dont le nombre de deficiences augmente, resident pour moitie dans les maisons d’accueil specialisees (MAS) et les foyers d’accueil medicalises (FAM). Aux personnes handicapees qui avancent en âge dans les etablissements et services medico-sociaux du champ du handicap, s’ajoutent celles avec un handicap reconnu avant 60 ans qui resident dans un etablissement pour personnes âgees : elles sont au moins 25 800 en 2015. Malgre les limites des enquetes, l’etude semble mettre en evidence trois parcours types en lien avec le processus de vieillissement : un parcours ou les personnes restent principalement hebergees a domicile tout en travaillant en ESAT ou en beneficiant d’un accompagnement, un autre ou elles sont principalement en institution et un dernier ou elles ont un handicap reconnu mais pas de contact avec les etablissements du champ du handicap. Les premieres entreraient frequemment en EHPA, mais pas directement apres avoir arrete de travailler en ESAT ou beneficie d’un service d’accompagnement. Les secondes, a mesure qu’elles deviendraient de plus en plus dependantes en avancant en âge, iraient d’etablissements pour personnes handicapees en etablissements pour personnes handicapees accueillant des personnes toujours plus dependantes. Les dernieres n’ont jamais vecu en institution et entrent en EHPA en vieillissant.

The reuse-recycling of objects and materials is a phenomenon frequently identified in ancient constructions. However, despite its apparent banality, archaeologists are not always able to recognize this practice. It can be seen and identified only when the material and its form and finishing deviate from the rest of the masonry. It then becomes evident and we are reminded of its ubiquity in buildings. Though the stages of the reuse-recycling process are difficult to perceive, this practice is not the result of random material recuperations. The materials are selected, as is their destination in the construction. The “choin de Fay” – a cold limestone extracted from the Bugey quarries – provides a well-identified example of reuse-recycling in the cities of Lyon and Vienne. Abundantly used in Antique monumental constructions, this stone with desirable qualities (ease of polishing, resistance to compression and frost, large pieces) was widely reused-recycled in Antiquity and throughout the Middle Ages. Based on a confrontation of more than 60 years of archaeological data and bibliographic sources, it was possible to reconstruct part of the chaîne opératoire (production sequence) from the recuperation of the material until its new use. This study thus reveals the diverse esthetic, technical and economic factors leading to reuse-recycling. It addresses questions concerning resource site ownership and the legal context surrounding these practices. The example of “choin de Fay” thus offers an opportunity to study the complexity of the practice of reuse-recycling., Le remploi – abordé comme la réutilisation ou le recyclage d’objets ou de matériaux variés – est un phénomène fréquemment rencontré, notamment dans l’analyse des constructions anciennes. Pratiqué de tout temps, il s’inscrit dans la chaîne opératoire ordi-naire de la construction. Malgré cette apparente banalité, le regard de l’archéologue ne peut pas toujours en saisir la présence. Il faut en effet qu’il revête un caractère manifeste: il se voit, se repère, lorsque son matériau, sa forme, sa finition, détonne avec le reste de la maçonnerie. Il devient alors évident et nous rappelle son omniprésence dans le bâti. Observé comme le résultat d’un processus dont on perçoit difficilement toutes les étapes, le remploi ne procède pourtant pas d’une récupération hasardeuse. Les matériaux sont choisis, tout comme leur destination dans la construction. À ce titre, le choin de Fay – calcaire froid extrait des carrières du Bugey (Ain) –, fournit un exemple de remploi bien identifié dans les villes de Lyon (Rhône) et de Vienne (Isère). Abondamment utilisée dans les constructions monumentales antiques, cette pierre aux qualités recherchées (facilité de polissage, résistance à la compression et au gel, modules de taille importante) est largement remployée dès l’Antiquité et tout au long du Moyen Âge. Le croisement de plus de 60ans de données archéologiques et de sources textuelles inédites permet de restituer une partie de la chaîne opératoire, depuis sa récupération jusqu’à sa nouvelle mise en œuvre. Son étude met en lumière la diversité des facteurs qui conduisent à ce remploi: ils sont esthétiques, techniques ou encore économiques. Elle permet de questionner la propriété des gisements et le contexte juridique qui encadre ces pratiques. Derrière l’exemple du choin de Fay, l’économie du remploi peut être ainsi abordée dans toute sa complexité.

This paper gives an overview of the Astronomical Light Optical Hybrid Analysis (ALOHA) project dedicated to investigate a new method for high resolution imaging in mid infrared astronomy. This proposal aims to use a non-linear frequency conversion process to shift the thermal infrared radiation to a shorter wavelength domain compatible with proven technology such as guided optics and detectors. After a description of the principle, we summarise the evolution of our study from the high flux seminal experiments to the latest results in the photon counting regime.

International audience

In the framework of the ALOHA project (Astronomical Light Optical Hybrid Analysis), devoted to high resolution imaging in the L band, we investigate in this paper the possibility to deploy fibre links between the telescopes of the CHARA Array. As a first step, we set up an outdoor hectometric fibre interferometer to measure the vibration environment at the Mount Wilson Observatory. The optical path difference of this interferometer has been actively stabilised within an accuracy better than 4 nmrms, a stability largely sufficient for any interferometric application.

International audience; In this paper, we propose a multichannel spectral configuration of the Astronomical Light Optical Hybrid Analysis (ALOHA) instrument dedicated to high resolution imaging. A frequency conversion process is implemented in each arm of an interferometer to transfer the astronomical light to a shorter wavelength domain. Exploiting the spectral selectivity of this non-linear optical process, we propose to use a set of independent pump lasers in order to simultaneously study multiple spectral channels. This principle is experimentally demonstrated with a dual-channel configuration as a proof-of-principle.

This paper deals with the effect of the telescope size on accuracy of the data acquisition in a optical fibre linked stellar interferometer. In this context we introduce the concept of antenna diagram commonly used for microwaves antennae. This concept is essential to explain the contrasts and the phaseclosure acquisitions corruption in a stellar interferometer. The telescope pointing errors induces additional effects that are superimposed with the field limitation and could become critical.

International audience; High resolution stellar interferometers are very powerful efficient instruments to get a better knowledge of our Universe through the spatial coherence analysis of the light. For this purpose, the optical fields collected by each telescope Ti are mixed together. From the interferometric pattern, two expected information called the contrast Cij and the phase information φij are extracted. These information lead to the Vij, called the complex visibility, with Vij=Cijexp(jφij). For each telescope doublet TiTj, it is possible to get a complex visibility Vij. The Zernike Van Cittert theorem gives a relationship between the intensity distribution of the object observed and the complex visibility. The combination of the acquired complex visibilities and a reconstruction algorithm allows imaging reconstruction. To avoid lots of technical difficulties related to infrared optics (components transmission, thermal noises, thermal cooling...), our team proposes to explore the possibility of using nonlinear optical techniques. This is a promising alternative detection technique for detecting infrared optical signals. This way, we experimentally demonstrate that frequency conversion does not result in additional bias on the interferometric data supplied by a stellar interferometer. In this presentation, we report on wavelength conversion of the light collected by each telescope from the infrared domain to the visible. The interferometric pattern is observed in the visible domain with our, so called, upconversion interferometer. Thereby, one can benefit from mature optical components mainly used in optical telecommunications (waveguide, coupler, multiplexer...) and efficient low-noise detection schemes up to the single-photon counting level.

International audience; Astronomical Light Optical Hybrid Analysis (ALOHA@3.39 µm) is a new instrumental concept designed for high angular resolution astronomical imaging in the L Band. The originality of our experimental device is to include a frequency conversion process in each arm of the interferometer that frequency shifts the mid infrared signal to the near infrared domain. This method relaxes the stringent limitations due to the thermal noise background radiated by the instrument itself. The aim of this paper is to estimate the current sensitivity limit of the instrument and validate the ability to provide calibrated contrasts with a quasi monochromatic signal. We demonstrate the possibility to measure fringe contrasts greater than 94.5% with a signal-to-noise ratio close to 7. The flux level at the input of each arm of the interferometer is then equal to 100 fW. This would correspond to a zero magnitude star in the L Band for a 1 m 2 telescope surface and a 3 nm converted spectral bandwidth.

In comparison to the radio and sub-millimetric domains, imaging with optical interferometry is still in its infancy. Due to the limited number of telescopes in existing arrays, image generation is a demanding process that relies on time-consuming reconfiguration of the interferometer array and super-synthesis. Using single mode optical fibres for the coherent transport of light from the collecting telescopes to the focal plane, a new generation of interferometers optimized for imaging can be designed. To support this claim, we report on the successful completion of the `OHANA Iki project: an end-to-end, on-sky demonstration of a two-telescope interferometer, built around near-infrared single mode fibres, carried out as part of the `OHANA project. Having demonstrated that coherent transport by single-mode fibres is feasible, we explore the concepts, performances, and limitations of a new imaging facility with single mode fibres at its heart: Agile Guided Interferometer for Longbaseline Imaging Synthesis (AGILIS). AGILIS has the potential of becoming a next generation facility or a precursor to a much larger project like the Planet Formation Imager (PFI)., 16 pages, 10 figures, 2 tables, accepted in A&A

At the time of the burgundian kingdom, religious construction in Lyon and Vienne greatly increased. Some ancient writers Sidoine Apollinaire, Avit of Vienne, Gregory of Tours, describe contemporary buildings with some accuracy and help us to understand the part played by bishops and also the links between the ideal conception of the building and material needs. The numerous excavations since 1970, some buildings still standing point to important differences in the religious buildings of the two towns, difference of plans, between buildings with a single nave or with three naves, the presence of a crypt or not, of a transept or not which could be explained by the existence of models.

International audience; In this paper we describe an upconversion detector in the mid infrared (around 3.5 μm). We take advantage of the PPLN ridge waveguide technology to achieve single photon detection at room temperature on a single spatial mode. With a pump power of 192 mW we obtain a detection efficiency of 0.4% for 22k dark count per second, which corresponds to a noise equivalent power of 3.0 fW · Hz−1/2 and an internal conversion efficiency of 85 %/W of pump.

International audience; In the context of new generation instruments for astronomical interferometer, we have developed in laboratory a new kind of optical interferometer using the frequency conversion of the star light. We investigate the sensitivity limit and reliability of our so-called upconversion interferometer when operating in photon counting mode. For this purpose, we have implemented a laboratory test bench including two three-arm interferometers dedicated to high angular resolution imaging. The first classical one works at the same wavelength as the laboratory star (infrared) and operates with high optical flux levels (used as a reference interferometer). The second one, under test, uses sum frequency generation process in a non-linear optical waveguide placed on each arm to shift the wavelength of the infrared laboratory star to the visible domain. The observables are obtained in photon counting operation, involving signal processing to recover unbiased data. The reference measurement (high flux complex visibilities in infrared) and the upconversion interferometer observables (complex visibilities obtained in photon counting regime) are in good agreement. We notice a degradation on the phase closure terms reliability for low values of the triple product (bispectrum). We estimate from the experimental results the related limiting magnitude for several configurations using an upconversion interferometer.

In the aim of access the high angular resolution for mid infrared observations, our team propose to include non linear processes on each arm of an interferometer. This project called ALOHA is now adapted for the L band detection, specially at 3.39 μm. Our team has previously published the first contrast measured in laboratory with such an up-conversion interferometer. The fringe contrast we measured was closed to the theoretical maximum at 100%. In a second step, we investigated the stability of the instrument over several months. The residual drifts are mainly due to the non real-time photometry monitoring.

The interferometric concept named ALOHA (Astronomical Light Optical Hybrid Analysis) offers an alternative for high resolution imaging in the mid-infrared domain by shifting the astronomical light to shorter wavelength where optical guided components from telecommunications are available and efficient. A prototype with two arms converting a signal from 1.55 μm to 630 nm is used to validate the concept in laboratory and on-sky. Thanks to collaboration with the CHARA team, photometric tests were achieved with a single arm of the interferometer and have allowed to predict instrument performance in its interferometric configuration in order to obtain first fringes in H band.

The ALOHA research program aims to propose a breakthrough generation of instrument for high resolution imaging in astronomy. This fully innovative concept results from our unique skills with a simultaneous competence in nonlinear optics and high resolution imaging with telescope arrays. Acting like a mixer in a radio receiver, the nonlinear process (sum frequency generation) shifts the infrared radiations emitted by the observed astrophysical source to a visible spectral domain. This way, the light beam is more easily processed by mature optical devices and detectors. The compatibility of the nonlinear process with the spatial coherence analysis has been successfully tested through preliminary in lab experiments. Now it’s time to apply this technique in a real astronomical environment. First on-sky results have been observed during the last missions at the CHARA Array.

The Astronomical Light Optical Hybrid Analysis project investigates the combined use of a telescope array interferometer and nonlinear optics to propose a new generation of instruments dedicated to high-resolution imaging for infrared astronomy. The nonlinear process of optical frequency conversion transfers the astronomical light to a shorter wavelength domain. Here, we report on the first fringes obtained on the sky with the prototype operated at 1.55 μm in the astronomical H band and implemented on the Center for High Angular Resolution Astronomy telescope array. This seminal result allows us to foresee a future extension to the challenging midinfrared spectral domain.