Bifunctional terahertz modulator for beam steering and broadband absorption based on a hybrid structure of graphene...

A bifunctional metamaterial is proposed based on a hybrid graphene and vanadium dioxide (VO₂) configuration, which can realize a dynamic switch between beam steering and broadband absorption. The structure consists of a VO₂ square, graphene patch, topas spacer, VO₂ film, topas spacer, and metal substrate. When VO₂ is in the metallic state, the structure serves as a coding metamaterial. By engineering different sizes of the top VO₂ square and adjusting the Fermi energy level of graphene, the incident wave is scattered in different patterns. When VO₂ is in the dielectric state, the structure serves as a broadband absorber. By changing the Fermi energy level of graphene from 0.0 eV to 0.9 eV, absorptance can be gradually changed and working bandwidth widens. There is an absorption band with near 100% absorptance from 0.9 THz to 1.35 THz when the Fermi energy level is 0.73 eV. And the designed broadband absorber is polarization-insensitive within the incident angle of 50°. Our work may show great potential in applications such as terahertz switching and modulation.