Miniaturized Multi-Spectral Perfect Metamaterial Absorber for THz Sensing, Imaging and Spectroscopic Applications

An ultra-thin terahertz (THz) perfect metamaterial (MM) absorber with multi-spectral characteristics is reported in this paper. The MM absorber has a compact geometry and is developed on a polyimide substrate supported by a silicon wafer. The conductive regions of the perfect MM absorber are created using copper. The MM absorber has a square lattice and the unit cell is patterned using concentric L-stubs connected to a central stub along one end of the L-sections. These structures are rotated and distributed along the four sides to obtain a polarization-independent absorber unit cell. The proposed absorber has six distinct frequency bands between 0.45 and 2.2 THz. The absorptivity in each of the frequency bands is greater than 90% with a peak absorption of 99% at 1 THz and 1.56 THz. The absorber is tested for angular independence and the performance is found stable up to 60°. Furthermore, the absorber as a material sensor is evaluated and the results are presented. The sensitivity of the sensor is estimated to be greater than 10.56 GHz/PU with a deviation of less than 3.12 GHz/μm. Thus, from the investigations presented, it is inferred that the proposed MM absorber meets the need for THz sensing, imaging and spectroscopy.