Quad band metal-dielectric-metal perfect absorber to selective sensing application

In this article, we have managed to achieve a quad-band perfect classical absorber in the terahertz band. In this proposed structure, which consists of three layers that the top and bottom layers made of gold and a dielectric layer, is located in middle layer. The results show that this structure has four perfect absorption bands with an average absorption of 98.22% at frequencies of 1.36, 2.6, 3.68, and 4.36 THz. To better understand the absorption mechanism, an equivalent circuit related to the proposed structure is presented. We have also shown that the percentage of absorption of the proposed absorber has increased due to the loss of the middle layer. Finally, the distribution of the electric fields is shown at each of the absorption frequencies. Due to its four bands, this absorber has potential in imaging, selective sensing, and photodetector applications.