Creation of Artificial Surface Conductivity on Metallic Metamaterials

Metal films with a periodic arrangement of cut-through slits are studied to show that artificial surface conductivity is created at the flat interface between the periodic slits and the cover/substrate. The presence of surface conductivity when the periodic structure is modeled by an effective refractive index can describe how non-specular higher diffracted orders affect the specular zeroth diffracted order. The magnitude of this surface conductivity is controlled geometrically. The artificial surface conductivity is pure imaginary and thus reactive if all non-specular orders are evanescent. This is usually the case in the low frequency regime. At higher working frequencies when some non-specular diffracted orders are non-evanescent, however, the artificial surface conductivity becomes complex and thus resistive. The power lost in the resistive part of the surface conductivity represents the power, which is carried away from the specular direction.