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Proceedings Paper

The integrated optics beam combiner assembly of the GRAVITY/VLTI instrument
Author(s): L. Jocou; K. Perraut; A. Nolot; T. Moulin; Y. Magnard; P. Labeye; V. Lapras; F. Eisenhauer; G. Perrin; A. Amorim; W. Brandner; C. Straubmeier
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Paper Abstract

Gravity aims at enhancing infrared imaging at VLTI to significantly improve our understanding of the physical processes related to gravitation and accretion within compact objects. With its fiber-fed integrated optics, infrared wavefront sensors, fringe tracker, beam stabilization and a novel metrology concept, GRAVITY will push the sensitivity and accuracy of astrometry and interferometric imaging far beyond what is offered today. Four telescopes will be combined in dual feed in the K band providing precision astrometry of order 10 micro-arcseconds, and imaging with 4- milliarcsecond resolution. The fringe tracker and the scientific instrument host an identical integrated optics beam combiner made by silica-on-silicon etching technology that is put inside a cryogenic vessel and cooled down to 200K to reduce thermal background and increase sensitivity. This paper gives the design of the integrated beam combiner and of its fibered array that allows feeding the combiner with stellar light. Lab measurement of spectral throughput and interferometric performance for beam combiners made by Flame Hydrolysis Deposition and by Plasma-Enhanced Chemical Vapor Deposition (PECVD) are given. The procedure to glue together the beam combiner and its fibered array is described as well as the tests to validate the performance and the ageing effects at low temperature. Finally the thermal analysis and the eigen-frequency study of the whole device are presented.

Paper Details

Date Published: 12 September 2012
PDF: 13 pages
Proc. SPIE 8445, Optical and Infrared Interferometry III, 84452X (12 September 2012); doi: 10.1117/12.925556
Show Author Affiliations
L. Jocou, UJF-Grenoble 1, CNRS-INSU, Institut de Planétologie et d'Astrophysique de Grenoble (France)
K. Perraut, UJF-Grenoble 1, CNRS-INSU, Institut de Planétologie et d'Astrophysique de Grenoble (France)
A. Nolot, UJF-Grenoble 1, CNRS-INSU, Institut de Planétologie et d'Astrophysique de Grenoble (France)
T. Moulin, UJF-Grenoble 1, CNRS-INSU, Institut de Planétologie et d'Astrophysique de Grenoble (France)
Y. Magnard, UJF-Grenoble 1, CNRS-INSU, Institut de Planétologie et d'Astrophysique de Grenoble (France)
P. Labeye, CEA-LETI Minatec (France)
V. Lapras, CEA-LETI Minatec (France)
F. Eisenhauer, Max-Planck-Institut für extraterrestrische Physik (Germany)
G. Perrin, LESIA - Observatoire de Paris, CNRS, Univ. Pierre et Marie Curie, Univ. Paris-Diderot (France)
A. Amorim, SIM (Portugal)
W. Brandner, Max-Planck-Institut für Astronomie (Germany)
C. Straubmeier, Univ. zu Köln (Germany)


Published in SPIE Proceedings Vol. 8445:
Optical and Infrared Interferometry III
Françoise Delplancke; Jayadev K. Rajagopal; Fabien Malbet, Editor(s)

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