Abstract
We design a double-sided perfect absorber at 2.4 THz within the terahertz gap to enable light absorption at the bidirectional directions, which is impossible for the traditional metamaterial-based perfect absorbers due to the employment of a metallic ground plane dedicated to reduce transmission. Here, the double-sided perfect absorber is fabricated on a λ 0 /6-thick polyethylene terephthalate (PET) substrate of ϵ r = 3.05×(1+0.08i) sandwiched by the two identical randomized metallic patterns, which provide equalized permittivity and permeability to match the impedance of free space and enormous imaginary part of refractive index to trap the light, evidenced by the retrieval method.