Fabrication and characterization of 115 GHz double split ring resonator

Electron paramagnetic resonance (EPR) spectroscopy requires an efficient coupling of electromagnetic waves over a sample volume. However, it is often challenging when EPR is operated in the terahertz (THz) range. Here, we report the fabrication and characterization of double split-ring resonators (DSRRs) designed to operate at a frequency of 115 GHz. The DSRR device consists of the outer and inner rings with diameters of 190 and 50 μm, respectively. Both rings have gaps, located on opposite sides, to concentrate and enhance the induced magnetic fields within the rings. The DSRR devices are fabricated using a wet-etch photolithography process. We also develop a characterization method to measure the resonant frequencies and Q-factors of individual DSRR devices. The developed DSRR fabrication method is useful for the development of resonators for various THz experiments.