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 (E F ) 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 E F 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 E F 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 E F of graphene. This work provides an alternative method for constructing multifunctional integrated THz devices based on graphene metamaterial.