Measurements of Stress-Optic Coefficients in the Transparent Regime of Solids
The lack of data on infrared stress-optic coefficients is due primarily to experimental difficulties in adapting existing methods, which were devised for measurements in the visible. This report describes a method readily adaptable to laser frequencies in both the visible and infrared, and sensitive enough for measurement of materials of low elastic limit, such as the alkali halides. We treat the specimen as a linear retarder and determine the phase change between two linearly polarized rays oriented parellel and perpendicular to the applied stress direction, from which the birefringence, q11−q12, and the constant q44 may be calculated. We report the results of measurements at 0.63μm and 10.6μm on a variety of solids, including alkali halides, alkaline earth fluorides, and chalcogenides.