Crystal orientation dependence of polarized infrared reflectance response of hexagonal sapphire crystal

Abstract Polarized infrared (IR) reflectance responses of c -, a - and r -plane sapphire crystals were investigated. The sapphire crystals with differently oriented surfaces exhibited different reststrahlen features. Except for c -plane sapphire, the polarized IR reflectance responses were sensitive to the orientation of the samples. The spectral features for a - and r -plane sapphire crystals were modulated by just rotating the samples about their surface normal. To analyze the observations, a theoretical model for the polarized IR reflectivity that considers the effects of crystal orientation of a hexagonal crystal system was employed. Overall, the theoretical predictions were in good agreement with experimental data. The crystal orientation information deduced from the polarized IR reflectance spectra is consistent with that acquired from X-ray diffraction measurements.