Investigation of electromagnetic properties of a high absorptive, weakly reflective metamaterial - Substrate system with compensated chirality

In the present paper, a theoretical and experimental study of a highly absorptive, weakly reflective coating designed and fabricated on the basis of 3D THz resonant elements is reported. Transmission and reflection of electromagnetic waves from the metamaterial-substrate structure involving a highly absorptive, weakly reflective array of artificial bi-anisotropic elements were analyzed. The samples contained paired right-handed and left-handed helices, due to the fact that the chirality was compensated. The parameters of helices were optimized to achieve roughly identical values of dielectric permittivity and magnetic permeability. As a result, the metamaterial exhibited weak reflectivity in the vicinity of resonance frequency. On the other hand, effective resonance properties of the helices were tuned to ensure substantial absorption of THz radiation. Analytical expressions for the coefficients of radiation reflection and transmission in the samples were derived by solving a boundary-value problem for the propagation of electromagnetic waves in the metamaterial-substrate system. Simulated properties of fabricated structures were compared with experimental data.