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.