Dual-band microwave resonators based on cross hollow structures for refractive index sensing

We numerically and experimentally studied the electromagnetic characteristics of a suitably designed planar metamaterial which composed of cross hollow structures. The results show that two sharp transmission dips with quality factors of 7.93 and 19.3 can be generated in the microwave region under the excitation of normal incident electromagnetic wave. And if its surface is covered by 2 mm thick analyte, both of the two transmission dips show linearly spectral shift with the change of the analytes' refractive index. Using the two resonances as the identifiers, the calculated average refractive index sensitivities are 1.116 GHz/refractive index unit (RIU) and 2.357 GHz/RIU, with corresponding figure of merits (FOM) of 1.87 and 4.9. It offers a potential for sensing detection and provides a reliable reference for the design of excellent plasmonic sensors.