21 research outputs found
Towards a Better Understanding of OPD Limitations for Higher Sensitivity and Contrast at the VLTI
Precise control of the optical path differences (OPD) in the Very Large
Telescope Interferometer (VLTI) was critical for the characterization of the
black hole at the center of our Galaxy - leading to the 2020 Nobel prize in
physics. There is now significant effort to push these OPD limits even further,
in-particular achieving 100nm OPD RMS on the 8m unit telescopes (UT's) to allow
higher contrast and sensitivity at the VLTI. This work calculated the
theoretical atmospheric OPD limit of the VLTI as 5nm and 15nm RMS, with current
levels around 200nm and 100nm RMS for the UT and 1.8m auxillary telescopes
(AT's) respectively, when using bright targets in good atmospheric conditions.
We find experimental evidence for the power law theoretically
predicted from the effect of telescope filtering in the case of the ATs which
is not currently observed for the UT's. Fitting a series of vibrating mirrors
modelled as dampened harmonic oscillators, we were able to model the UT OPD PSD
of the gravity fringe tracker to RMSE up to 100Hz, which could
adequately explain a hidden power law on the UTs. Vibration
frequencies in the range of 60-90Hz and also 40-50Hz were found to generally
dominate the closed loop OPD residuals of Gravity. Cross correlating
accelerometer with Gravity data, it was found that strong contributions in the
40-50Hz range are coming from the M1-M3 mirrors, while a significant portion of
power from the 60-100Hz contributions are likely coming from between the
M4-M10. From the vibrating mirror model it was shown that achieving sub 100nm
OPD RMS for particular baselines (that have OPD200nm RMS) required
removing nearly all vibration sources below 100Hz
VLTI status update: a decade of operations and beyond
We present the latest update of the European Southern Observatory's Very
Large Telescope interferometer (VLTI). The operations of VLTI have greatly
improved in the past years: reduction of the execution time; better offering of
telescopes configurations; improvements on AMBER limiting magnitudes; study of
polarization effects and control for single mode fibres; fringe tracking real
time data, etc. We present some of these improvements and also quantify the
operational improvements using a performance metric. We take the opportunity of
the first decade of operations to reflect on the VLTI community which is
analyzed quantitatively and qualitatively. Finally, we present briefly the
preparatory work for the arrival of the second generation instruments GRAVITY
and MATISSE.Comment: 10 pages, 7 figures, Proceedings of the SPIE, 9146-1
The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI
The GRAVITY instrument has been revolutionary for near-infrared
interferometry by pushing sensitivity and precision to previously unknown
limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer
(VLTI) in GRAVITY+, these limits will be pushed even further, with vastly
improved sky coverage, as well as faint-science and high-contrast capabilities.
This upgrade includes the implementation of wide-field off-axis
fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser
guide stars in an upgraded facility. GRAVITY+ will open up the sky to the
measurement of black hole masses across cosmic time in hundreds of active
galactic nuclei, use the faint stars in the Galactic centre to probe General
Relativity, and enable the characterisation of dozens of young exoplanets to
study their formation, bearing the promise of another scientific revolution to
come at the VLTI.Comment: Published in the ESO Messenge
L-band nulling interferometry at the VLTI with Asgard/NOTT: status and plans
editorial reviewedNOTT (formerly Hi-5) is the L’-band (3.5-4.0 μm) nulling interferometer of Asgard, an instrument suite in preparation for the VLTI visitor focus. The primary scientific objectives of NOTT include characterizing (i) young planetary systems near the snow line, a critical region for giant planet formation, and (ii) nearby mainsequence stars close to the habitable zone, with a focus on detecting exozodiacal dust that could obscure Earthlike
planets. In 2023-2024, the final warm optics have been procured and assembled in a new laboratory at KU Leuven. First fringes and null measurements were obtained using a Gallium Lanthanum Sulfide (GLS) photonic chip that was also tested at cryogenic temperatures. In this paper, we present an overall update of the NOTT project with a particular focus on the cold mechanical design, the first results in the laboratory with the final NOTT warm optics, and the ongoing Asgard integration activities. We also report on other ongoing activities such as the characterization of the photonic chip (GLS, LiNbO3, SiO), the development of the exoplanet science case, the design of the dispersion control module, and the progress with the self-calibration data reduction software.SCIF
Sources lasers stabilisées sur un peigne de fréquence pour la mesure de distances absolues au sein du très grand téléscope interférométrique européen
PRIMA, un futur instrument du VLTI, utilise un système de métrologie laser pour mesurer les variations de chemin optique internes à l'interféromètre. L'étude présentée dans ce mémoire porte sur le développement, l'intégration et le test de sources lasersThe forthcoming instrument of the Very Large Telescope Interferometer (VLTI), called Phase-Referenced Imaging and Micro-arcsecond Astrometry facility (PRIMA), uses a laser metrology system to monitor the variations of internal path lengths. This disserta
Sources lasers stabilisées sur un peigne de fréquence pour la mesure de distances absolues au sein du très grand téléscope interférométrique européen
PRIMA, un futur instrument du VLTI, utilise un système de métrologie laser pour mesurer les variations de chemin optique internes à l'interféromètre. L'étude présentée dans ce mémoire porte sur le développement, l'intégration et le test de sources lasers stabilisées en fréquence pour ce système de métrologie. Dans une première partie, nous présentons le cahier des charges du système dans le contexte de PRIMA et du VLTI. Nous rappelons les bases de l'interférométrie laser et les problèmes qu impose son application à PRIMA. Nous en déduisons la nécessité de stabiliser la longueur d'onde du laser sur une référence absolue et exposons l'intérêt de transformer ce système en un système de mesure de distances absolues.Dans une seconde partie, nous décrivons notre contribution à la stabilisation en fréquence d'un laser Nd:YAG sur une raie d'absorption de l'iode. Nous mesurons précisément les performances du système avec un peigne de fréquences optiques auto-référencé. Nous améliorons le système pour satisfaire aux exigences du cahier des charges.La troisième partie est consacrée à la transformation du système en un système de mesure de distances absolues par l'utilisation de l'interférométrie à deux longueurs d'onde. Nous proposons un nouveau concept de source laser qui utilise un peigne de fréquences optiques comme référence de fréquence. Cette source permet de générer un choix sans précédent de longueurs d'onde synthétiques avec une précision relative dans le vide meilleure que 10 11. Nous validons le concept sur un prototype et montrons qu il peut être utilisé en interférométrie à deux longueurs d'onde pour résoudre une longueur d'onde optique.The forthcoming instrument of the Very Large Telescope Interferometer (VLTI), called Phase-Referenced Imaging and Micro-arcsecond Astrometry facility (PRIMA), uses a laser metrology system to monitor the variations of internal path lengths. This dissertation addresses the development, integration and test of frquency stabilized laser sources for the PRIMA Metrology system (PRIMET).In the first part, we present in the context of PRIMA and the VLTI the specifications of PRIMET. We recall the basics of single-wavelength laser interferometry and introduce the problems raised by its application to PRIMET. We present the need for the absolute frquency stabilization of PRIMET laser and the interest for an upgrade of PRIMET towards absolute distance measurements.In the second part, we present our contribution to the absolute frquency stabilization of PRIMET Nd:YAG laser on a transition of iodine. We characterize the system and measure precisely its performance with a self-referenced optical frquency comb. We improve the system to reach the specifications in terms of accuracy and stability of the locking frquency.The third part addresses the upgrade of PRIMET towards absolute distance measurements by the use of two-wavelength interferometry. We propose a new concept of two-wavelength laser source frquency stabilized on an optical frquency comb. This permits the generation of an unprecedented large choice of synthetic wavelength with a relative accuracy better than 10 11 in vacuum. We validate the concept on a prototype and shows that it can be used to resolve an optical wavelength. Finally, we propose to apply this concept to the upgrade of PRIMET
Sources lasers stabilisées sur un peigne de fréquence pour la mesure de distances absolues au sein du très grand téléscope interférométrique européen
PRIMA, un futur instrument du VLTI, utilise un système de métrologie laser pour mesurer les variations de chemin optique internes à l interféromètre. L étude présentée dans ce mémoire porte sur le développement, l intégration et le test de sources lasers stabilisées en fréquence pour ce système de métrologie. Dans une première partie, nous présentons le cahier des charges du système dans le contexte de PRIMA et du VLTI. Nous rappelons les bases de l interférométrie laser et les problèmes qu impose son application à PRIMA. Nous en déduisons la nécessité de stabiliser la longueur d onde du laser sur une référence absolue et exposons l intérêt de transformer ce système en un système de mesure de distances absolues.Dans une seconde partie, nous décrivons notre contribution à la stabilisation en fréquence d un laser Nd:YAG sur une raie d absorption de l iode. Nous mesurons précisément les performances du système avec un peigne de fréquences optiques auto-référencé. Nous améliorons le système pour satisfaire aux exigences du cahier des charges.La troisième partie est consacrée à la transformation du système en un système de mesure de distances absolues par l utilisation de l interférométrie à deux longueurs d onde. Nous proposons un nouveau concept de source laser qui utilise un peigne de fréquences optiques comme référence de fréquence. Cette source permet de générer un choix sans précédent de longueurs d onde synthétiques avec une précision relative dans le vide meilleure que 10 11. Nous validons le concept sur un prototype et montrons qu il peut être utilisé en interférométrie à deux longueurs d onde pour résoudre une longueur d onde optique.The forthcoming instrument of the Very Large Telescope Interferometer (VLTI), called Phase-Referenced Imaging and Micro-arcsecond Astrometry facility (PRIMA), uses a laser metrology system to monitor the variations of internal path lengths. This dissertation addresses the development, integration and test of frequency stabilized laser sources for the PRIMA Metrology system (PRIMET).In the first part, we present in the context of PRIMA and the VLTI the specifications of PRIMET. We recall the basics of single-wavelength laser interferometry and introduce the problems raised by its application to PRIMET. We present the need for the absolute frequency stabilization of PRIMET laser and the interest for an upgrade of PRIMET towards absolute distance measurements.In the second part, we present our contribution to the absolute frequency stabilization of PRIMET Nd:YAG laser on a transition of iodine. We characterize the system and measure precisely its performance with a self-referenced optical frequency comb. We improve the system to reach the specifications in terms of accuracy and stability of the locking frequency.The third part addresses the upgrade of PRIMET towards absolute distance measurements by the use of two-wavelength interferometry. We propose a new concept of two-wavelength laser source frequency stabilized on an optical frequency comb. This permits the generation of an unprecedented large choice of synthetic wavelength with a relative accuracy better than 10 11 in vacuum. We validate the concept on a prototype and shows that it can be used to resolve an optical wavelength. Finally, we propose to apply this concept to the upgrade of PRIMET.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF