WGM resonator-based measurement technique for weakly and highly absorbing substances

We present the main peculiarities of the accurate microwave techniques for measuring the surface impedance properties of unconventional superconductors and the complex permittivity of biochemical liquids. The samples under test are substances with very small and very high losses of microwave energy. The techniques are developed by authors on the basis of high-Q whispering-gallery mode sapphire resonators of different geometry. The developed techniques allow measuring superconductors in forms of both large-area unpatterned films (up to 50mm diameter) and small single crystals (about 2×2×0.1mm³). They allow also measuring liquids under test of sub-microliter/nanoliter volumes. The authors underline a fundamental difference in the finding characteristics of the two types of substances which differ greatly by levels of microwave losses. Experimental data are obtained in Ka-band.