Millimeter-Wave Surface Impedance Characterization of HTS Films and Single Crystals Using Quasi-Optical Sapphire Resonators

High-Q sapphire quasi-optical dielectric resonators (QDRs) excited on whispering-gallery modes are key techniques for accurate characterization in millimeter (mm) wavelength range of surface impedance of HTS large-area films and can be useful for impedance characterization of small HTS single crystals, including various unconventional superconductors. Hemispherical QDR-based technique for mm impedance characterization of HTS films is analysed theoretically and confirmed experimentally. Such an approach can be applied to QDR of modified forms. The temperature dependences of the YBaCuO films resistance properties using hemispherical resonator and the iron-pnictide single-crystal impedance properties using radially-slotted one are measured in Ka-band.