Quasi-optical sapphire resonators for millimeter wave impedance characterization of high-TC superconducting thin films

A number of whispering gallery mode (WGM) dielectric resonators or quasi-optical dielectric resonators (QDR) are proposed by authors for high-temperature superconducting film surface resistance measurement in millimeter wavelength range. Results of comparing advantages and disadvantages of the resonators of three types are presented. The resonators were made of single crystal sapphire in the forms of cylindrical disk, truncated cone and hemisphere with a purpose of work in Ka-band. The peculiarities of resonance frequency spectra, field distribution and interaction of microwave field with the sample under test are considered. In authorspsila opinion each of the resonators has own niche for application.