Graphene metamaterial-based broadband/dual-narrowband switchable terahertz absorber with adjustable absorptivity and large phase shift

Abstract

We present a graphene metamaterial-based broadband/dual-narrowband switchable terahertz (THz) absorber with adjustable absorptivity and large phase shift. From top to bottom of the device, there are graphene-metal hybrid pattern, silicon dioxide layer, silicon layer and metal substrate. When the Fermi energy (EF) of graphene is equal to 0 eV, it has two narrowband absorption peaks at frequencies of 1.88 THz and 2.54 THz, respectively. However, when the EF is equal to 0.8 eV, it turns to a broadband absorber in the frequency range from 1.60 to 2.42 THz. Moreover, if the EF increases from 0.2 eV to 0.8 eV, its absorptivity can be dynamically adjusted from 60% to more than 90% in a broadband of 0.82 THz. Most importantly, the absorber can also dynamically control the phase shift. In the frequency range of 2.04 THz to 2.34 THz, a maximum dynamic phase shift of 192 degrees is achieved by changing the EF of graphene. This work provides an alternative method for constructing multifunctional integrated THz devices based on graphene metamaterial.