Anisotropic behaviour and negative refraction in stacked subwavelength hole arrays metamaterials

Oblique incidence on a stack of subwavelength hole arrays wafers is analyzed both from simulation and measurement. A strong anisotropic behaviour is observed giving as a result that for P-polarized illumination, the refracted beam emerges at negative angles whereas for S-polarized illumination it is at positive angles. Two-dimensional dispersion diagrams are calculated to predict qualitatively the performance of the structure in terms of the refraction, which is subsequently demonstrated with experiments in the millimetre-wave range.