Tunable enhanced bandwidth all-graphene -dielectric terahertz metamaterial absorber/reflector

Abstract

We report an all-graphene-dielectric terahertz metamaterial absorber/reflector, whose absorption bandwidth and absorptivity can be tuned by applying the bias voltage to regulate the Fermi energy of the patterned graphene. When no bias voltage is applied, it acts as a reflector; when regulating the bias voltage applied to the different parts of the patterned graphene, its bandwidth of over 90 % absorptivity can be increased to 1.75 THz, correspond to relative absorption bandwidth to 60.9 %.The mechanism for tunable enhanced absorption bandwidth is analyzed through the impedance matching and the surface current distributions. In addition, the broadband absorber is insensitive to both the polarization angle and the incident angle. Our research provides a candidate for designing tunable broadband graphene-based absorbers in terahertz frequencies.