Numerical investigation of broadband THz metamaterial absorber with double composite structure layer

A broadband terahertz (THz) metamaterial absorber (MA) based on a double composite structure layer on a metallic board is proposed. Each layer consists of four different sized square metallic plates. The absorbing properties and variation laws have been numerically investigated with FDTD method. The numerical results show that the absorber bandwidth is 0.642 THz with the central frequency around 1.901 THz. The physical mechanism of the broadband absorber can be explained as the overlapping of eight closely resonance frequencies using the analysis of magnetic field distribution. Besides, the proposed absorber has several advantages, including the polarization insensitive, large angle tolerance and potential to be applied for integrated THz photoelectric devices.