Photoelasticity is considered a useful measurement tool for non-destructive and contactless determination of mechanical stresses or strains in the production of silicon wafers. In this work, a detailed derivation for the anisotropic stress-optic law is presented, and the corresponding stress-optical parameters are measured.

The inline monitoring of parameters in aqueous liquids is facing an increasing demand in many application areas. In this paper we report on an optical monitoring of the pH value in liquids by means of a sensitive hydrogel, which can be applied in the physiological range. Our results indicate a nearly linear dependency between pH value and hydrogel swelling. Furthermore, we show an improvement of the response time by a factor of 2 in comparison to other systems exploiting this kind of hydrogel.

The continuous monitoring of industrial and environmental processes is becoming an increasingly important aspect with both economic and societal impact. To realize this task, spectral-optical sensors with their outstanding properties in terms of sensitivity and reliability are a potential solution. However, for exploiting these sensors in a cost- and energy-efficient sensing system, a miniaturized readout unit is needed. Here we present a card-size, inexpensive, and robust readout electronics.