Anisotropy of Dielectric Losses in Al2O3 and SiO2 Single Crystals

The procedure and results of measurements of the dielectric loss tangent using the dielectric resonator technique on azimuthal modes of the HE (quasi-E) and EH (quasi-H) types are considered. The measurements were performed for uniaxial anisotropic single crystals of Al2O3 (at a frequency of 11 GHz) and SiO2 (at 39 GHz) in a temperature range of 80-373 K and for an isotropic single crystal of Y3Al5O2 (YAG) at room temperature in a frequency range of 9-15 GHz. The proposed method revealed the anisotropy of dielectric losses in Al2O3 and SiO2 single crystals in the temperature range studied. According to this, losses along the optical axis of these crystals are lower than in the transverse plane. In the YAG crystal, the Q values for modes of the two types with the same frequency are close, which corresponds to isotropic losses. The dielectric losses in YAG increase in proportion to the frequency.