Multiband polarization insensitive and tunable terahertz metamaterial perfect absorber based on the heterogeneous structure of graphene

In this paper, we present and investigate a multi-band metamaterial perfect absorber based on the heterogeneous structure of graphene with Cu and SiO2 substrates. The top layer of structure consists of one graphene disk at the center and four graphene solid triangle with semicircular cuts on them that surround the central disk. This heterogeneous structure causes us to achieve 99.5%, 99.7%, 94.71% and 97.06% perfect absorptions peaks at 4.24 THz, 5.89 THz, 9.66 THz and 10.62 THz, respectively. The absorption mechanism based on electric fields has been investigated. We can shift the wavelength of absorption peaks to our required wavelength by changing the Fermi level (mu(c)) of graphene. Two absorption peaks of this absorber remain unchanged in different light incident angles. In addition, very important point about this structure is that it is not sensitive to polarization and this feature makes the proposed absorber very suitable for applications such as imaging, filtering, sensing and detecting applications.