Tunable Cavity-based Chiral Microwave 3D-helical Metamaterial

The paper is devoted to the study of chiral metamaterials based on three-dimensional helices. Particular attention is paid to tunable structures embedded into the Fabry-Perot resonator formed by plane-parallel silicon wafers. Numerical simulations show the control of the polarization plane rotation angle as well as ellipticity of the transmitted wave by tuning the thickness of the resonator in a wide spectral range. The influence of the resonator was demonstrated in an experiment at 35 GHz using a metamaterial formed by a hybrid technology based on 3D-printing, molding and shadow metal deposition. It is shown that the enhancement of chiral effects in the long-wavelength region could be explained by the anisotropy helical grid structures. The advantage of the proposed metamaterial is control by changing resonator cavity, not parameters of the resonant metal elements. The results obtained are promising for the creation of tunable systems for controlling the polarization in the microwave range.