Effective properties of terahertz double split-ring resonators at oblique incidence

By combining experimental and theoretical efforts we study the optical properties of single-layer, double split-ring resonators at oblique incidences for terahertz frequencies and reveal their angular dependent effective properties. Contrary to what is usually anticipated, for incidence angles deviating from normal we do not observe any significant dispersion in the effective permeability. Effective properties are dominated instead by a strong dispersion in the effective permittivity, causing also the wavenumber in the medium to be large. The structure is shown to possess almost invariant effective properties for oblique incidences. (C) 2009 Optical Society of America