The calibration of the vector polarimeter POLIS

TL;DR

This thesis details the calibration process of the POLIS vector polarimeter, including instrument setup, measurement techniques, and calibration procedures, aimed at accurate polarization measurements in solar physics.

Contribution

It provides a comprehensive calibration methodology for POLIS, including instrumental calibration and polarimetric modeling, with detailed descriptions suitable for educational purposes.

Findings

Calibration data set evaluation for instrument accuracy

Detailed polarimetric model of the telescope

Methodology for polarization measurement in solar observations

Abstract

In this diploma thesis, the calibration of the vector polarimeter POLIS will be described. The instrument is built by the Kiepenheuer-Institut fuer Sonnenphysik (Freiburg/Germany) in cooperation with the High Altitude Observatory (Boulder/USA) and will be operated at the German Vacuum Tower Telescope in Tenerife. The instrument yields simultaneously the polarization state of light in two spectral ranges at 396 nm and 630 nm. The measurement is performed with a rotating retarder, which modulates the incident polarization. The modulation is transformed into a varying intensity through polarizing beamsplitters. The demodulation uses a weighted integration scheme to obtain the full Stokes vector of the radiation. The calibration of the polarimeter is performed through the evaluation of a calibration data set produced with a calibration unit consisting of a linear polarizer and a retarder. The instrumental calibration and the polarimetric model of the telescope are described in detail. This document is an unaltered version of my diploma thesis from 2002. Parts of it have been re-used in later publications, but in a very compressed way removing a lot of details. Its currrent intended use would be as introductory literature to polarimetry and its application in solar physics for students. I have used it a few times already for exactly this purpose.