Index of Refraction of ZnO

Abstract

Measurements of the refractive indices of ZnO single crystals are extended from room down to liquid-helium temperatures in the region between the absorption edge and 5500 Å for E⊥C and E∥C. The indices are calculated from the locations of interference maxima in transmission spectra caused by multiple reflections in thin (0.4–80 μ), plane-parallel platelets. The dispersion curves at room temperature are similar to those reported by Mollwo, but they are extended to include the optical isotropic point. At energies near absorption edge n∥<n⊥, while in the long wavelength region n∥>n⊥, as is found in other II-VI materials of the wurtzite symmetry. The isotropic point and its variation with temperature was also determined by birefringence measurements.