Terahertz absorber based on double-layer graphene metasurface with tunable absorption window and intensity

Although the designing of graphene-based tunable broadband terahertz (THz) absorbers are relatively developed, it is rarely described how to establish linkages between the absorption window and intensity tunability. Here, an ultra-compact double-layer graphene metasurface based absorber (GMSA) has been numerically designed using the finite integration technique (FIT) method, in which two graphene layers play the roles of absorption window modulation layer and absorption intensity modulation layer by exploiting the electrically tunable property of graphene, respectively. Detailed mechanistic analysis shows that due to the transition from Fabry-Perot resonance (FPR) to graphene surface plasmon resonance (GSPR), the proposed structure enables a dynamically tunable shift from low-frequency broadband absorption (“L-BA”) state to high-frequency broadband absorption (“H-BA”) state within 4.47 THz, while the absorption intensity of both states can be independently continuously adjusted from low to high. Moreover, the absorption window can be tuned easily by changing the structural parameters, and the structure shows an excellent broadband absorption property for both TE and TM-polarized waves over a wide range of oblique incidence angles of 60°. All the findings indicate that the proposed GMSA is promising for detection, imaging, and object cloaking in the THz regime.