Extraordinary terahertz transmission through a double-layer metal array with closed ring resonators

• We design a terahertz metamaterial composed of metal-dielectric-metal, which consists of metallic layers with an air hole array and one coaxial closed ring resonator in the air hole.
• We have provided an explanation of the transmission characteristics by means of the surface plasmon polaritons (SPPs) and magnetic polaritons (MP) resonance based on the distribution of the surface current.
• The equivalent LC circuit models of the structure are set up based on the MP resonances.
• The effects of the geometric parameters on the transmission peaks are studied by the equivalent LC circuit models.

In this paper, we numerically investigate the transmission properties of a terahertz metamaterial. This metamaterial is composed of metal-dielectric-metal, which consists of metallic layers with an air hole array and one coaxial closed ring resonator in the air hole. The metamaterial in the THz range of 0.2–1 THz has three transmission peaks. We provide an explanation of the transmission peaks by means of the surface plasmon polaritons and magnetic polaritons resonance based on the distribution of the surface current. Then according to the magnetic polaritons resonance, the equivalent circuit model of the metamaterial is established. The effects of geometric parameters on the transmission peaks are discussed and studied by an equivalent circuit model and surface plasmon polaritons dispersion relation. Our metamaterial promises dual-band potential applications such as filters.