Terahertz absorption modulator with largely tunable bandwidth and intensity

A dual-tunable metamaterial absorption modulator is proposed based on a hybrid vanadium dioxide-graphene configuration. When vanadium dioxide is in the state of metal, the design serves as a narrowband absorber. It is composed of vanadium dioxide patch, topas spacer, and vanadium dioxide film. When vanadium dioxide is in the state of dielectric, the design serves as a broadband absorber. It includes vanadium dioxide patch, topas spacer, graphene layer, vanadium dioxide film, topas spacer, metal substrate. By adjusting Fermi level of graphene from 0.1 eV to 0.7 eV, absorptance of the proposed absorber can be dynamically tuned from 45.3% to 94.5% at 0.4 THz and from 31% to 96.3% at 1.0 THz, and absorption bandwidth gradually widens. Because of the unique dielectric to metal transition properties of vanadium dioxide, the tunable behavior of absorption frequency and intensity can be achieved through external stimuli. Thus our design can realize adjustable absorption of intensity and frequency in terahertz range. Besides, the designed narrowband and broadband absorbers are polarization-insensitive for small incident angle due to the symmetry, and absorptions of the design keep good performance within the angle range of 50°.