Wideband Chiral Metamaterial for Polarization Conversion Based on Helical-Type Inclusions

Materials with a high electromagnetic activity usually present a strong resonant response that produces extreme values for the constitutive parameters, but in a narrow frequency range. Here, a chiral material composed by four helical-like resonators, as the unit cell, able to produce high rotatory dispersion and low circular dichroism in a wide frequency band is presented. The transmission and reflection coefficients of a thin slab of such material have been determined using a free-wave experimental setup and numerical simulations. The experimental results show a cross-polarization conversion in the transmission mode for linearly polarized incident waves in a 2-GHz bandwidth centered at 10 GHz and a polarization conversion ratio larger than 0.97.