Additional boundary condition for the wire medium

In this paper, it is proved that the continuity of the tangential components of the average electric and magnetic fields is insufficient to describe the reflection of plane waves by a set of thin parallel wires embedded in a dielectric host using a homogenization approach. Based on physical arguments a new boundary condition is proposed to characterize the scattering of waves by the homogenized wire medium. In order to further support the proposed theory, the problem of reflection of a plane wave by a set of semi-infinite parallel wires is solved analytically within the thin-wire approximation. Extensive numerical simulations demonstrate that when the additional boundary condition is considered the agreement between full wave results and homogenization theory is very good even for wavelengths comparable with the lattice constant.