WGM Resonators for Conductivity Measurements of Graphene Films

The response of sapphire WGM resonator to a single-layer graphene introduced onto the dielectric substrate is studied in Ka-band. The experimental investigations were performed for two types of resonator modes: HE and EH. The modes differ by the prevailing component: electric or magnetic of electromagnetic field along the resonator longitudinal axis. The possibility of using these modes for finding graphene conductivity is demonstrated. Based on the experimental and the resonator model data obtained using COMSOL Multiphysics software the graphene conductivity values were obtained. The conductivity values calculated based on results of measurements performed on two mode types with different substrate position relative to the resonator are compared. The results demonstrate reproducibility. The possible source of some difference between the results obtained on different modes is discussed. The recommendations regarding the design of the most suitable configuration for graphene conductivity measurements are proposed.