Multi-angle spectrophotometric reflectance methods for determining refractive indices

The experience of developing and applying methods for measuring the refractive coefficients of crystals of the highest and middle categories based on multi-angle spectrophotometric reflection methods is presented: by the reflection spectrum from one face at an angle of incidence of light close to normal, and by the reflection method when light falls at Brewster angle. The advantages and limitations of the methods and the requirements for the samples are described. It is shown that the reflection method at an angle of incidence close to normal is applicable for optically isotropic media. The Brewster angle method is applicable for crystals of the highest and middle categories. The measurement accuracy of both methods has been determined. The applicability of these methods is shown for samples of crystals of the highest and middle categories Gd3Al2Ga3O12:Ce and La3Ga5.5Ta0.5O14 respectively.