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Proceedings Paper

Birefringence compensation in PIONIER
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Paper Abstract

In an optical interferometer, the phase of astronomical signals is corrupted not only by the Earth’s atmosphere, but also by instrumental artifacts, among which birefringence, that affects the relative phase of two orthogonal polarizations. Instrumental birefringence occurs at each mirror reflection, but can also occur in the instrument where the signals are recombined., especially when optical fibers are used on the signal path. We present here a new technique to cancel instrumental birefringence, in the context of the PIONIER instrument at the VLTI (ESO, Paranal observatory). This is achieved by introducing in each of the beams a birefringent plate with an adjustable inclination, that allows to cancel the differential birefringence between the beams before recombination. We present our derivation of the amount of birefringence introduced by such an inclined plate. We show the actual performance achieved with the Pionier instrument. The initial alignment takes of order of one hour, and is stable for several days. Tweaking is performed at the beginning of each observing run and takes approximately fifteen minutes. We demonstrate a simple and effective technique to cancel differential birefringence in interferometric instruments. This technique should be applicable to second generation VLTI instruments.

Paper Details

Date Published: 12 September 2012
PDF: 11 pages
Proc. SPIE 8445, Optical and Infrared Interferometry III, 84452W (12 September 2012); doi: 10.1117/12.925421
Show Author Affiliations
Bernard Lazareff, Institut de Planétologie et d'Astrophysique de Grenoble, OSUG, Univ. Joseph Fourier (France)
Jean-Baptiste Le Bouquin, Institut de Planétologie et d'Astrophysique de Grenoble, OSUG, Univ. Joseph Fourier (France)
Jean-Philippe Berger, European Southern Observatory (Chile)
Laurent Jocou, Institut de Planétologie et d'Astrophysique de Grenoble, OSUG, Univ. Joseph Fourier (France)
Pierre Kern, Institut de Planétologie et d'Astrophysique de Grenoble, OSUG, Univ. Joseph Fourier (France)
Gérard Zins, Institut de Planétologie et d'Astrophysique de Grenoble, OSUG, Univ. Joseph Fourier (France)


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

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