Design of a seven-band perfect metamaterial absorber for THz sensing applications

This paper presents the design of a perfect metamaterial absorber tera-Hertz (THz) frequencies. The proposed absorber is developed using a square loop enclosing a highly convoluted swastika element. The arms of the swastika elements are coiled to create a square spiral configuration to increase the electrical length of the resonator without increasing the size of the unit cell absorber. The proposed unit cell has multiabsorption characteristics with absorption peaks at 0.82, 1, 1.24, 1.54, 1.85, 2.2 and 2.5 THz. The corresponding absorptivity is greater than 80% in all the reported frequencies. The electrical size of the proposed absorber is 0.42λeff × 0.42λeff, where λeff is the effective wavelength calculated at 0.82 THz. The proposed absorber has structural symmetry and has identical absorption spectra for both TE and TM modes of operation. The angular stability is investigated, and the performance is stable for the angles of incidence up to 70°. The proposed absorber has a small frequency ratio and can be used for THz material sensing. The prototype absorber as a sensor is simulated, and the results are presented.