A spectroscopic multi-angle probe of metamaterial permeability

We present spectroscopic data for acute-angle reflection and transmission of two planar metamaterial samples, one at microwave frequencies and one at far-infrared frequencies. We show that the observed evolution of the magnetic resonance with the increasing angle of incidence is in quantitative agreement with the Fresnel expressions. This finding uncovers a convenient approach towards the retrieval of optical constants of metamaterials by fitting the Fresnel theory to multiple angle-datasets simultaneously; thus obviating the need for phase information. Physically reasonable values for the magnetic permeability are recovered by this no-phase fitting in the case of both the microwave and infrared metamaterials.