Bridging terahertz metal slot antenna with parameterized electrical conductivity: insights from finite element method and microscopic theory

Metal slot antennas exhibit high transmission characteristics at resonant frequencies when electromagnetic waves with polarization in the width direction of the rectangular hole structure enter, having wavelengths approximately twice the length of the rectangular hole. In this study, we utilize COMSOL multiphysics simulation to examine the transmission behaviors of such resonators operating in terahertz frequency range, with a specific emphasis on their performance when incorporating micron-sized conductive embedding within the central region of the rectangular slot. We observe that as the conductivity of the embedding material increases, the resonant frequency undergoes a shift towards higher values through non-resonant behaviors in the intermediate conductivity range, eventually reaching nearly twice the fundamental resonant mode. The additional analytic microscopic calculation reveals that the interference effect of the electromagnetic field inside the slot antenna can be responsible for the transmittance modifications and provides a reference for investigating unknown embedded targets. These findings provide valuable insights into the versatile applications of metal slot antennas, particularly in areas such as sensing and detection of subwavelength materials.