Piezo-optic properties of LiNH4SO4 crystals

The effect of uniaxial stresses applied along the principle crystallographic directions on the dispersion and temperature dependences of birefringence of LiNH4SO4 crystals is studied. The anomalies of the temperature dependence of birefringence near 220 K have been observed, and their position is shown to depend on the magnitude and direction of crystal uniaxial compression. The spectral and temperature dependences of combined piezo-optic coefficients πim0 of these crystals are investigated. It is demonstrated that these coefficients have different signs, are characterized by significant dispersion, and weakly change with temperature; they also have equal absolute values in the vicinity of the isotropic point.