In-lab ALOHA mid-infrared up-conversion interferometer in the photon counting regime @λ = 3.39 µm

International audienceAstronomical Light Optical Hybrid Analysis ([email protected] 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

First test on Photonic Crystal Fiber potential for broadband interferometry

International audienceThe Photonic Crystal Fibers (PCFs) are microstructured waveguides currently developed in the frame of metrology, non-linear optics or coherent tomography. PCF studies are mainly focused on the improvement of dispersion property and wide spectral single-mode operating domain. Consequently, in the astronomical context, this kind of fiber is a good candidate to design a fiber linked version of stellar interferometer for aperture synthesis. In this paper, we study the potential of these fibers taking advantage of the wide spectral single-mode operation. We propose an experimental setup acting as a two-beam interferometer using PCFs to measure fringes contrasts at four different wavelengths (670nm, 980nm, 1328nm and 1543nm) corresponding to R, I, J and H astronomical bands with the same couple of PCFs. For this purpose, we implement for the first time a piezoelectric PCF optical path modulator

Multichannel spectral mode of the ALOHA up-conversion interferometer

International audienceIn 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

Induction of Phlorotannins and Gene Expression in the Brown Macroalga Fucus vesiculosus in Response to the Herbivore Littorina littorea

Mechanisms related to the induction of phlorotannin biosynthesis in marine brown algae remain poorly known. Several studies undertaken on fucoid species have shown that phlorotannins accumulate in the algae for several days or weeks after being exposed to grazing, and this is measured by direct quantification of soluble phenolic compounds. In order to investigate earlier inducible responses involved in phlorotannin metabolism, Fucus vesiculosus was studied between 6 and 72 h of grazing by the sea snail Littorina littorea. In this study, the quantification of soluble phenolic compounds was complemented by a Quantitative real-time PCR (qRT-PCR) approach applied on genes that are potentially involved in either the phlorotannin metabolism or stress responses. Soluble phlorotannin levels remained stable during the kinetics and increased significantly only after 12 h in the presence of grazers, compared to the control, before decreasing to the initial steady state for the rest of the kinetics. Under grazing conditions, the expression of vbpo, cyp450 and ast6 genes was upregulated, respectively, at 6 h, 12 h and 24 h, and cyp450 gene was downregulated after 72 h. Interestingly, the pksIII gene involved in the synthesis of phloroglucinol was overexpressed under grazing conditions after 24 h and 72 h. This study supports the hypothesis that phlorotannins are able to provide an inducible chemical defense under grazing activity, which is regulated at different stages of the stress response

Design of a Tunable Subwavelength Plasma-Based Resonator for Electrically Small Antenna Applications in L-band

A preliminary study of the design of an electrically small plasma-based resonator using a localized surface plasmon resonance (LSPR) above 1 GHz is presented. Such a resonator is intended to be used to develop an electrically small antenna with frequency agility. This resonator consists of a plasma discharge confined in a hemispherical glass shell 3 cm in diameter on a ground plane. From 1 to 1.5 GHz, the plasma electron density required to achieve the LSPR must be between 0.5 × 1011 and 1.4×1011 cm−3. Plasma losses are taken into account in this study and provide information on the required gas pressure. Typically for neon gas, the working pressure must be around 50 mTorr. A practical implementation using a miniature inductively coupled plasma (mICP) source is finally discussed

Genetic diversity and taxonomic aspects of wild carrot in France

If in France, genetic resources of cultivated carrot are well studied and preserved, the wild compartment of the species remains unknown and underutilized, while there are many populations of wild carrot on the French territory. Several collecting missions were undertaken from 2009 to 2013 to identify and collect populations, particularly in coastal areas, in continental France and Corsica. More than a hundred populations were collected, with a good distribution throughout the territory, and eleven taxa were identified. The status of these taxa is variable, with some very common and others underrepresented or specific to a given area. Morphological and molecular studies are developed in order to improve the knowledge of taxonomy and diversity. The study conducted with microsatellite markers showed a high genetic diversity at the intra-and inter-populations levels. The overall results show that the Mediterranean coast and Corsica exhibit a particularly high diversity. The work confirms the specific interest of some populations and the taxonomic separation into 2 subgroups carota and gummifer in Daucus carota L. This study will allow developing a strategy for management of genetic resources and their valorisation in breeding