Numerical analysis of the terahertz multilayer metamaterials

On the basis of transfer matrix method (TMM), the effective medium theories (EMT) which can be applied to the n-layer unit cell structures have been developed. By using this method, we have systematically investigated the influences of the structure parameters, operation frequency, and material gain on the dispersion properties and transmission of the metallic-dielectric stratified structure (MDSS) in the terahertz (THz) regime. The n-unit cell structures show much more freedom to study the MDSS. The results show that the dispersion relationship acquired from the EMT agrees well with those from the TMM when the value of k(x) is small. With the increase of the frequency, the n-layer unit cell MDSS can show more than one dip, and the dip positions can be changed by altering the doping concentration of the InSb layer. As the material gain increase, the transmission increases, and the full-width-half-maximum of the transmission spectrum decrease. This proposed method can also be applied to other spectral regions, such as microwave and infrared regimes. The results are beneficial to improve the performance of MDSSs devices and have great potential for many applications in fields of sub-wavelength image and superlens design.