Experimental verification of isotropic and polarization properties of high permittivity-based metamaterial

We report on the experimental verification of isotropy and polarization properties of high-permittivity metamaterial composed of cubic ferroelectric resonators. Barium strontium titanate (BST) with permittivity as high as 850 is used as ferroelectrics material so that the metamaterial condition is fulfilled. The isotropy was investigated via the scattering of an electromagnetic wave under tilted incidence. From the experimental data, we observed that the magnetic resonance, at 8.6 GHz for a millimeter cube size, is independent of the incidence angle for the TM and TE polarizations. For the latter, however, an extra dip in the transmittance at higher frequency (10.7 GHz for a period of 1.2 mm), not evident under normal incidence, is found. By comparing the full wave simulations of microstructured and homogenous metamaterial slabs it is shown that the electromagnetic response is independent of the underlying structuring technique. On this basis, we verified that this extra dip, theoretically predicted by [Koschny et al., Phys. Rev. B 71, 121103(R) (2005)] for a three-dimensional split ring resonator technology, results from the permeability dispersion characteristics of BST cubes, with zero transmittance at the magnetic plasma frequency.