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Water isotopes measurements in polar ice cores are key to reconstruct past climatic variations. However, the relationship between surface temperature and water isotopic composition is not straightforward because snow isotopic composition is influenced by many factors in addition to local temperature of condensation (evaporation origin, trajectory of moist air, post deposition effects). In order to refine this interpretation, parallel observation of water vapor and surface snow isotopic composition in polar regions is essential.Measuring atmospheric water isotopic composition is however an important challenge, especially in dry places like the East Antarctic plateau, where water mixing ratio can be as low as 10 ppmv. Laser spectrometers based on the cavity ring-down spectroscopy (CRDS), commonly used for field measurement, fail to precisely measure water vapor isotopic composition for the lower range of water mixing ratios recorded in East Antarctica.The optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) technique offers an interesting alternative for low humidity detection. During the austral summer 2022 – 2023, two OF-CEAS spectrometers were respectively installed at Dumont-d’Urville, situated along the coast, and Dome C, situated on the plateau, at 3230 m above sea level. We present here results obtained with this OF-CEAS technique, which shows an improved limit of detection, while keeping a low humidity dependence.This work is part of the AWACA ERC project, in which we intend to install several OF-CEAS instruments, in three remote sites situated along the Dumont-d’Urville – Dome C transect, in addition to the two permanent polar stations., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Dome C is located on the high Antarctic plateau, at 3233m above sea level, and 1200km away from the coastline. At this location, the EPICA ice core was retrieved from the ice sheet and allowed the reconstruction of past climatic information 800,000 years back in time. Amongst several atmospheric parameters, the past local temperature was inferred from the stable water isotope record measured in the ice.To interpret this record, it is necessary to understand how it was formed in such a dry and cold environment. This includes understanding the water cycle dynamics in Antarctica, from evaporation to precipitation and moisture pathways, as well as the processes affecting the record after deposition of the precipitation, such as snow-atmosphere exchanges.During the austral summer 2018-2019, a Picarro laser spectrometer was installed on site to monitor continuously the isotopic composition of the atmosphere. It provided measurements for all austral summers since then and allowed the detection of two major atmospheric river events, including a rare event during the onset of the cold Antarctic winter. To go beyond the limitations of the Picarro instrument when measuring at very low humidity levels, as encountered during the wintertime at Dome C, a new laser spectrometer dedicated to low humidity measurements has been developed and installed it in parallel to the Picarro instrument during the summer season 2022-2023. Here we present the results of the atmospheric isotopic composition during four consecutive austral summers and the comparison of the two laser instruments during the most recent period., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The invention relates to a device and method for detecting an acoustic wave propagating toward a membrane, the membrane carrying a waveguide comprising an optical cavity defining a resonant frequency. Under the effect of a vibration of the membrane, the resonance frequency of the optical cavity varies. The device includes a light source for directing a light wave into the optical cavity, and a servo circuit for servo-controlling the wavelength of the light wave to the resonant wavelength of the optical cavity. Monitoring the variation in the wavelength of the light wave allows an amplitude of the acoustic wave to be estimated.

The invention is a device and method for detecting an analyte in a medium. An exciting light source produces an exciting light wave, which propagates to the medium and heats the latter. The device comprises a transducer for detecting the heating of the medium. According to one embodiment, the transducer is a thermal transducer, configured to detect a variation in the temperature of the medium. According to another embodiment, the transducer is an acoustic transducer, configured to detect a photoacoustic wave propagating from the medium. Whatever the embodiment, the transducer employs a membrane, on which a waveguide is placed. The waveguide comprises a resonant optical cavity. Transduction is achieved by analyzing a variation in a resonant wavelength of the optical cavity.

N° et date de publication de la demande : FR3105824 - 02/07/2021 (BOPI 2021-26)N° et date de dépôt : FR1915695 - 27/12/2019; L'invention est un dispositif et un procédé de détection d'une onde acoustique se propageant vers une membrane, la membrane supportant un guide d'onde comportant une cavité optique définissant une fréquence de résonance. Sous l'effet d'une vibration de la membrane la fréquence de résonance de la cavité optique varie. Le dispositif comporte une source de lumière pour diriger une onde lumineuse dans le cavité optique ainsi qu'un circuit d'asservissement pour asservir la longueur d'onde de l'onde lumineuse à la longueur d'onde de résonance de la cavité optique. Le suivi de la variation de la longueur d'onde de l'onde lumineuse permet d'estimer une amplitude de l'onde acoustique.

N° et date de publication de la demande : FR3105827 - 02/07/2021 (BOPI 2021-26)N° et date de dépôt : FR1915696 - 27/12/2019; L'invention est un dispositif et un procédé pour détecter un analyte dans un milieu. Une source de lumière d'excitation produit une onde lumineuse d'excitation, laquelle se propage vers le milieu en produisant un échauffement de ce dernier. Le dispositif comporte un transducteur pour détecter l'échauffement du milieu. Selon un mode de réalisation, le transducteur est un transducteur thermique, configuré pour détecter une variation de la température du milieu. Selon un autre mode de réalisation, le transducteur est un transducteur acoustique, configuré pour détecter une onde photoacoustique se propageant depuis le milieu. Quel que soit le mode de réalisation, le transducteur met en œuvre une membrane, sur laquelle est disposé un guide d'onde. Le guide d'onde comporte une cavité optique résonante. La transduction est réalisée en analysant une variation d'une longueur d'onde de résonance de la cavité optique.

International audience; A highly sensitive optical transduction system suitable for photoacoustic trace gas detection is presented. The system includes a thin deformable hinged cantilever assembled on an optical fiber to form a Fabry-Perot cavity, whose length varies according to the acoustic pressure disturbance. Consequently, the optical power of the reflected light fluctuates at acoustic frequencies around the working point, which is stabilized to prevent from environmental drift of the interference fringes. The resonant mechanical structure proposed in this study shows a spectral response in good agreement with FEM simulation, good linearity and stability, with a noise equivalent pressure of 12 $\mu$Pa/√Hz.