Systematische Untersuchung des Faraday-Effekts in der messtechnischen Anwendung

This dissertation systematically investigates the magneto-optical Faraday effect with regard to its metrological application. The primary objective is to provide a sound assessment of the potential, challenges, and limitations of the measurement principle for a given application. Secondary, new technical contributions to real-world applications are presented. The Faraday effect describes the rotation of the polarization plane of linearly polarized light within a transparent medium in the presence of a magnetic field. The rotation angle depends on the magnetic flux density in the direction of light propagation, the optical path length in the medium, and the material-specific Verdet constant. The change in rotation can be converted into a change in illuminance using a polarization filter. Conversely, a comparatively simple photodetection with a known Verdet constant allows for traceability to the exciting magnetic field and its causes (magnetometric application) or, with known magnetic excitation, to the rotation behavior and the medium composition (polarimetric application). The investigation of the phenomenon is embedded in three applications that demonstrate the breadth of applications, illuminate different aspects, and have current technical relevance. The investigated topics involve precise one-dimensional measurements of magnetic patterns in banknote security threads, fast measurements of two-dimensional magnetization patterns in the context of audio tapes the polarimetric use of the measurement setup based on the determination of the components of vegetable oils.