SPHERE / ZIMPOL: characterization of the FLC polarization modulator

摘要

ZIMPOL is an imaging polarimeter for the high-contrast SPHERE/VLT "planet finder" instrument using fastpolarization modulation and demodulating CCD detectors. The polarimetric performance of the ZIMPOL instrumentdepends on the polarimetric alignment and quality of the polarization components. This paper gives an overview on thepolarimetric concept and the calibration plan of ZIMPOL. We discuss in particular the alignment of the polarimetriccalibration components and the polarimetric properties of the ferro-electric liquid crystal (FLC) modulator package usedin ZIMPOL. Our measurements demonstrate the good broad-band performance of the modulator. Faint targets, likeextra-solar planets, require mainly a high polarimetric efficiency while for detailed studies of bright targets a goodcharacterization of the modulator package is essential. Therefore we quantify in detail the wavelength dependence of thepolarimetric efficiency and the cross-talk effects which have to be taken into account in the calibration and datareduction process of high S/N measurements.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.