Berlin 2024 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 61: Liquid and Amorphous Materials III

MM 61.2: Vortrag

Donnerstag, 21. März 2024, 15:45–16:00, C 243

Evaluation of optical anisotropy on the surface of stressed glass using a reflective polarimetric setup — •Felix Müller, Hainer Wackerbarth, and Georgios Ctistis — Institut für Nanophotonik Göttingen, Hans-Adolf-Krebs-Weg 1, 37077 Göttingen

The rising requirements on glass in its wide range of usage embrace stability and functionality. An important factor to achieve these is the precise adjustment of desired or undesired residual stress corresponding to the application. In order to determine surface stress with a non-contact, non-destructive and automatable method we have come up with a polarimetric approach. In contrast to the well-established transmission polarimetry, the challenge to be surface sensitive demands a much higher resolution of polarisation states and a more complicated measurement data analysis due to the oblique incidence. We have managed to distinguish surface stress differences in the range of 1 MPa by applying external stress for different orientations of two of the principle axes in the surface plane. Furthermore we have reached a spatial resolution of the laser spot size of 1 mm and are able to scan qualitative stress maps on certain areas of the sample’s surface. The polarimetric surface stress measurement considers the relation between the incoming and outgoing polarisation state. A comparison enables to refer the measured state to the material’s reflection properties, as described by a reflection matrix in the Müller-Stokes-formalism. Therefore, quantifying surface stress from those measurements underlies, additionally to a sufficient set of measured parameters, the relation between the Fresnel reflection matrix and the type and reason of the sample’s anisotropy.

Keywords: photoelasticity; polarimetry; surface stress; reflection; optical anisotropy