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Proceedings Paper

SPHERE / ZIMPOL: characterization of the FLC polarization modulator
Author(s): Andreas Bazzon; Daniel Gisler; Ronald Roelfsema; Hans M. Schmid; Johan Pragt; Eddy Elswijk; Menno de Haan; Mark Downing; Bernardo Salasnich; Alexey Pavlov; Jean-Luc Beuzit; Kjetil Dohlen; David Mouillet; François Wildi
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Paper Abstract

ZIMPOL is an imaging polarimeter for the high-contrast SPHERE/VLT "planet finder" instrument using fast polarization modulation and demodulating CCD detectors. The polarimetric performance of the ZIMPOL instrument depends on the polarimetric alignment and quality of the polarization components. This paper gives an overview on the polarimetric concept and the calibration plan of ZIMPOL. We discuss in particular the alignment of the polarimetric calibration components and the polarimetric properties of the ferro-electric liquid crystal (FLC) modulator package used in ZIMPOL. Our measurements demonstrate the good broad-band performance of the modulator. Faint targets, like extra-solar planets, require mainly a high polarimetric efficiency while for detailed studies of bright targets a good characterization of the modulator package is essential. Therefore we quantify in detail the wavelength dependence of the polarimetric efficiency and the cross-talk effects which have to be taken into account in the calibration and data reduction process of high S/N measurements.

Paper Details

Date Published: 24 September 2012
PDF: 14 pages
Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 844693 (24 September 2012); doi: 10.1117/12.925973
Show Author Affiliations
Andreas Bazzon, ETH Zürich (Switzerland)
Daniel Gisler, ETH Zürich (Switzerland)
Ronald Roelfsema, NOVA - ASTRON (Netherlands)
Hans M. Schmid, ETH Zürich (Switzerland)
Johan Pragt, NOVA - ASTRON (Netherlands)
Eddy Elswijk, NOVA - ASTRON (Netherlands)
Menno de Haan, NOVA - ASTRON (Netherlands)
Mark Downing, European Southern Observatory (Germany)
Bernardo Salasnich, INAF - Osservatorio Astronomico di Padova (Italy)
Alexey Pavlov, Max-Planck-Institut für Astronomie (Germany)
Jean-Luc Beuzit, Institut de Planetologie et d'Astrophysique de Grenoble, Univ. Joseph Fourier (France)
Kjetil Dohlen, Lab. d'Astrophysique de Marseille, Observatoire Astronomique de Marseille-Provence (France)
David Mouillet, Institut de Planetologie et d'Astrophysique de Grenoble, Univ. Joseph Fourier (France)
François Wildi, Observatoire de l'Univ. de Genève (Switzerland)

Published in SPIE Proceedings Vol. 8446:
Ground-based and Airborne Instrumentation for Astronomy IV
Ian S. McLean; Suzanne K. Ramsay; Hideki Takami, Editor(s)

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