Design and performance evaluation of flexible terahertz ultra-wideband stop-band filters.

This paper, to the best of our knowledge, introduces a novel ultra-wideband stop-band filter based on the metal-dielectric-metal structure. The filter makes use of flexible polydimethylsiloxane as the dielectric material, leveraging its high refractive index to achieve the desired filter benefits with minimal loss. For the metal layers, we combine copper with gold, thereby saving costs and reducing the oxidation of the copper. The filter has been simulated with the CST EM Studio Suite software. The simulation results show that the center frequency of the filter is 1.64 THz, its -20 bandwidth is 1.80 THz, the stop-band reflection exceeds 95%, and the square ratio is 0.93. We discuss the influence of the main structural parameters and the metal layer number on the transmission characteristics. The validity of the simulation results was verified through the analysis of the effective dielectric constant and magnetic permeability. To further understand the filtering mechanism, we conducted a comprehensive analysis and verification of the electric field intensity and surface current distribution. Additionally, the symmetry of the structure ensures the polarization insensitivity of the filter when electromagnetic waves are incident in the normal direction. The designed filter may have potential applications in terahertz communication, sensors, and electromagnetic shielding.