Tunable Broadband Terahertz Absorber Based on Triangular-Patterned Graphene with Sandwich Configuration

A terahertz (THz) metamaterial broadband perfect absorber featuring a simple sandwich structure with a top layer composed of a triangular-patterned graphene film is presented. The graphene pattern is designed to exhibit a pronounced surface plasmon resonance (SPR) effect, which locally enhances the internal electric field’s intensity, leading to broadband absorption of 2.8 THz above 90% and a peak absorption rate of 99.99% at 6.05 THz. The broadband tunability of the absorber was further investigated by modulating the Fermi level of the graphene, demonstrating an adjustment in the absorption rate from 6.18% to 99.99% via an external voltage. This study shows that the absorber demonstrates excellent angular tolerance by maintaining an absorption rate above 90% across incident angles ranging from 0° to 50°. The absorber’s broadband perfect absorption properties were examined using relative impedance theory. Additionally, to reveal the fundamental physics behind this absorption, detailed analyses of the electric field distributions were carried out. Consequently, the origin of the absorption peaks is elucidated. This absorber enables noise suppression for optoelectronic integration and THz communications.