A polarization insensitive miniaturized pentaband metamaterial THz absorber for material sensing applications

The design of a novel THz metamaterial absorber (MTM-A) with the miniaturized size is proposed in this paper. The proposed MTM-A is developed on a lossy polyimide substrate. The unit cell consists of a square loop connecting four highly convoluted, zig-zag shaped structures distributed along with the corners. The proposed MTM-A is small-sized with a footprint of 0.169λ_eff × 0.169λ_eff where λ_eff is the effective wavelength calculated at the lowest operating frequency. The proposed MTM-A offers five absorption peaks at 0.34 THz, 0.57 THz, 0.98 THz, 1.30 THz and 1.81 THz with absorption peaks greater than 90% in all the operating bands. The MTM-A exhibits rotational symmetry and hence it is polarization insensitive and has good angular stability up to 90°. The utilization of the proposed MTM-A as a material sensor is presented. The calculated sensitivity is greater than 6 GHz per permittivity unit with the highest sensitivity of 51.475 GHz/PU at 1.81 THz. The deviation in sensitivity for changing analyte thickness is less than 2.2 GHz/μm in all five absorption frequencies.