Ultra-Broadband Terahertz Absorbers Based on 4 x 4 Cascaded Metal-Dielectric Pairs

We present an ultra-broadband metamaterial absorber in the terahertz regime based on the proposed 4 x 4 cascaded metal-dielectric pairs, which would help to reduce the demand for fabrication precision. The generation mechanism of electromagnetic resonances and the formation process of the ultra-broadband absorption were investigated by finite-difference time-domain (FDTD) method. Numerical results showed that absorptivity of similar to 92 % was obtained between 3.2 and 11.8 THz using the 4 x 4 structure. Such absorber was one of potential candidates for rough terahertz frequency estimator with an average detection resolution of 0.56 THz within a 9-THz range, which could be a supplement to the active terahertz spectrum analyzers with high resolution but limited measurement range (similar to 1 THz).