SPHERE / ZIMPOL: characterization of the FLC polarization modulator

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

doi:10.1117/12.925973

24 September 2012 SPHERE / ZIMPOL: characterization of the FLC polarization modulator

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

Author Affiliations +

Proceedings Volume 8446, Ground-based and Airborne Instrumentation for Astronomy IV; 844693 (2012) https://doi.org/10.1117/12.925973
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

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.

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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, and François Wildi "SPHERE / ZIMPOL: characterization of the FLC polarization modulator", Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 844693 (24 September 2012); https://doi.org/10.1117/12.925973

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