Whispering gallery modes in rutile resonators at millimeter wave frequencies

Whispering gallery modes in single crystal rutile resonator were measured at the frequency range 15-30 GHz. Predicted and measured values of resonant frequencies for several WGM were in excellent agreement. Permittivity components parallel and perpendicular to anisotropy axis have been evaluated and their values were ε_⊥=85.8±0.2% and ε_||=163.2±0.2% at room temperature and frequencies 15-30 GHz. Dielectric loss tangent components of rutile measured at room temperature and frequency of 25 GHz were tanδ_⊥=4.2×10^-4±10% and tanδ_||=5.7×10^-4±10%