We demonstrated a multi-band plasmonic metamaterial absorber (MA), based on the near-field coupled resonators. In addition to the individual resonances of resonators in the proposed structure, which were split-ring resonator (SRR) and cross-shape structures, another resonance was also excited owing to the coupling of resonators, revealing a triple-band absorption. Furthermore, to control the absorption behavior, on the top of the SRRs, the identical SRRs made of graphene ink were pasted. By increasing the resistance of graphene ink, the coupling strength was weakened, changing the triple-band absorption to a dual-band one. Our work might be useful as the controllable devices, based on graphene-integrated plasmonic MA, such as filters, detectors and energy harvesters.

In this paper, a multifunctional metamaterial (MM) structure capable of performing as a polarization converter and absorber is proposed. By using DC bias voltage to control the capacitor of the integrated varactor, the near-field coupling in our structure can be manipulated to flexibly switch between polarization conversion (PC) mode and perfect absorption (PA) mode. The numerical simulation results show that in PC mode the polarization conversion ratio exceeds 90 % at 4 GHz, while the dual-band absorption is observed in PA mode with a value close to 90 % at 3.5 and 5.5 GHz. In addition, we also reduce the geometric sizes of the proposed structure to further examine its performance in the THz frequency range. Owing to its excellent characteristics in both PA and PC modes, the proposed hybrid MM structure is promising to apply in many fields such as radar, remote sensing, and satellite.