Dielectric waveguide resonator with a superconductive boundary layer

Dielectric waveguide resonators have been shown to exhibit high Q´s, limited by the dielectric loss. High-resonator Q is desirable in measuring the microwave attenuation of superconducting materials. The properties of a dielectric waveguide resonator with a superconductive boundary layer have been investigated. The microwave properties of YBaCuO and NbN thin films have been investigated by employing them as boundary layers on the dielectric waveguide. Transmission and reflection measure measurements on the dielectric waveguide resonator were performed from 20-40 GHz using a vector network analyzer. The temperature dependence of the loaded Q of the resonator was measured under weak coupling. The loaded Q-factors of the DWG resonator were measured to be as high as 12000 with a YBaCuO boundary and 20000 with an NbN boundary layer. The measured Q-factors were instrumentation limited in the superconducting state and represent a lower bound on the Q of the resonators. The results were found to be in agreement with the predictions of the Drude model for T⩾T_c and the Mattis-Bardeen theory for T⩽T_c