Power handling capabilities of Y-Ba-Cu-O wafers and patterned microstrip resonators

Epitaxially grown large area YBa₂Cu₃O_7-δ (YBCO) thin films are promising for the application in passive microwave devices (e.g. resonators, filters, antennas). The main criteria for these applications are low microwave losses and good power handling capabilities of the devices. Various measurement techniques are in use for the evaluation of the power handling capabilities of YBCO thin films. However, only few studies exist relating their results to the actual performance of the microwave devices. We investigate the rf field dependence of the surface resistance of YBCO thin films using a dielectric resonator technique at 8.5 GHz and 77 K. The lateral homogeneity of the films with respect to the surface resistance is analyzed with an open resonator technique at 145 GHz and 77 K. Subsequently the films are patterned to microstrip resonators and their quality factors are measured at 4 GHz and 77 K as a function of the input rf power. The results show that the low values of the surface resistance and its constant level up to high rf magnetic fields ~10 mT are necessary requirements but not stringent criteria for good power handling capability of the microstrip resonators