Anisotropy of the Refractive Indices and Thermal Expansion Coefficients of Rb2ZnCl4 Crystals

Abstract

The temperature dependences of the optical path difference ∆_і(Т) and relative changes δl_і/l_і in the thickness of Rb₂ZnCl₄ crystals have been studied. The temperature dependences of the relative changes in the refractive indices δn_і/(n_і – 1) are calculated. The critical index of the temperature changes in the refractive indices is estimated to be β = 0.31 ± 0.02, a value that is well consistent with the Landau theory of phase transitions. The coefficients of anisotropy of refractive indices А_n – 1(Т) are calculated. A characteristic minimum near the phase transition temperature is found in these dependences.