Characterization of a half wave plate and a polarizer for accurate starlight polarimetry

In the process of developing a space-based imaging Stokes polarimeter for starlight polarization measurements, we established a procedure to characterize its two main optical components: the wave plate and the polarizer. We demonstrate that a simple optical bench setup combined with a custom calibration procedure can be used to measure the non-ideality parameters of both the polarizer and the wave plate. Using this approach, we characterized two high-quality components for the V-band. We set an upper limit for the cross-polarization of the polarizer, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_B \le 1 \times 10<^>{-4}$$\end{document}, and a limit of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta \le 2 \times 10<^>{-4}$$\end{document} for the transmission imbalance of the half-wave plate. We show that with these components the setup yields reproducible measurements at the level of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.001\%$$\end{document} for the polarization degree of a weakly polarized source, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3'$$\end{document} for the position angle. We also investigate the performance of the components under tilted incidence, up to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$6<^>o$$\end{document} off-axis, as required for a wide-field imaging version of a stellar polarimeter. We find that within this range, even without any off-axis bias correction, these components enable measurements of the polarization degree with an accuracy better than 0.005, and of the polarization angle with an accuracy better than \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1<^>o$$\end{document}.