Refractive index homogeneity of large scale potassium dihydrogen phosphate crystal

Abstract

By using a traditional temperature reduction method, a large scale potassium dihydrogen phosphate (KDP) crystal is prepared. The refractive indices of different parts of this as-grown crystal are measured at 12 wavelengths between 0.253 and 1.530 um by using the new generation measuring instrument with an accuracy of 10-6. The measurement results show that refractive indices are inhomogenous in different parts of the large scale KDP crystal. The refractive index of the selected part close to the recovery area of crystal is smaller than that of selected part far from the recovery area. The deviation is on the order of 10-5-10-4. The refractive index inhomogeneity is related to the difference in crystalline quality among different parts in large KDP crystal. Furthermore, our measured data are compared with those in the literature published previously and the difference between them is analyzed. Meanwhile, by using root mean square method, numerical fitting to Sellmeier equation is conducted.