A polarization-insensitive and omnidirectional broadband terahertz metamaterial absorber based on coplanar multi-squares films

A simple design of terahertz metamaterial absorber (MA) based on a periodic array of square copper films was investigated numerically. The perfect narrow absorption mainly originates from magnetic polariton excitation and perfect impedance-match. The perfect absorbing properties of this simple design could be tunable by changing the side length based on equivalent LC resonance circuit mode. The bandwidth of the perfect absorption can be effectively enhanced by simply patterning different dimension elements with appropriate geometrical parameters on a coplanar. Finally, the absorption of the composite structure MA is greater than 90% and near perfect impedance-match to the free space in the frequency ranges of 6.24–7.04 THz. Further numerical simulations also demonstrate that the MA could achieve very high absorptivity at wide angles of incidence and polarization for both TE and TM waves.

► We proposed an ultra-thin terahertz metamaterial absorber based on a square films.
► The perfect absorbing properties could be tunable.
► The absorption bandwidth could be extended effectively.
► The full FWHM and the absorption bandwidth of 90% could achieve 2.1 THz and 0.8 THz.