Measurement of orientation dependent stress-optic coefficient of GaAs single crystals

The stress-optic coefficient C for (001) and (111) GaAs single crystal wafers at various observation directions was measured precisely using a simple four-point bending technique. Our experimental values of C for (001) GaAs wafers vary from $0.65×10−12 cm2/dyn$ (at 〈100〉 directions) to $1.43×10−12 cm2/dyn$ (at 〈110〉 directions). For (111) GaAs wafers, the experimental values of C show much smaller dependence on the observation direction and vary from $1.97×10−12 cm2/dyn$ (at 〈112〉 directions) to $2.11×10−12 cm2/dyn$ (at 〈110〉 directions). The combinations of piezo-optic coefficients $π11–π12$ and $π44$ were also derived from C for GaAs.