Ultrathin polarization-insensitive tri-band THz perfect metamaterial absorber

In this paper, an ultrathin and polarization-insensitive THz perfect metamaterial absorber (PMA) was proposed using the traditional sandwiched structure with circular patch resonators on the top layer. The simulated spectrum shows that the proposed PMA has three distinctive absorption peaks at f1 = 0.8 THz, f2 = 2.28 THz and f3 = 3.62 THz, with absorbance of 96.7%, 97.9% and 99.8%, respectively. The electric field distributions of the PMA reveal that the absorption mainly originates from the standing wave resonances between the top and bottom layers. The proposed PMA is polarization insensitive due to its axisymmetric unit cell structure. By adjusting the structure parameters, the resonance frequency, intensity and Q-factor of absorption peak can be tuned effectively. Our design may find potential applications in THz imaging, sensing and signal detection.