Terahertz Dual-Band Near-Zero Effective Index Metamaterial Based on Double-Sided Metal Microstructure

The zero-refractive-index metamaterials have excellent electromagnetic properties, which provide new ideas and methods to realize the control of electromagnetic waves and the design of new photoelectric devices. Here, we propose a double-sided metamaterial structure to achieve double-zero refractive index in the terahertz region. We use the S parameter inversion algorithm to extract the equivalent electromagnetic parameters of the metamaterial. By optimizing the design of structural parameters, we show that the effective refractive index can be achieved to be near zero at 0.5 - 1.7 THz and at 2.7 - 3.4 THz. By monitoring the current density distribution and the near-field distribution on the surface of the structure, we prove that the metamaterial structure has obvious zero refractive index effect at 1.66 and 3.34 THz. In addition, the influence of geometric parameters of metamaterial structures on equivalent refractive index is revealed.