Behaviour of subwavelength vs propagating holes in ET based prisms

In this work a comparison is established between a prism constructed by stacking perforated plates that support extraordinary transmission (ET) and another on constructed by stacking standard perforated plates with holes operating in propagation. The dispersion diagrams for both structures are calculated and from these a negative refractive index is predicted for ET plates, being positive for standard perforated plates. The simulated three-dimensional farfield patters show that main beam is at negative angles in the first case and at positive angles in the second case. Experiments performed in the millimetre wave range demonstrate negative refraction for the prism fabricated with ET plates and positive refraction for the prism fabricated with standard perforated plates.