Homogenization of bi-anisotropic metasurfaces.

Ultrathin metamaterial layers are modeled by a homogeneous bi-anisotropic film to represent various kinds of broken symmetries in photonic nanostructures, and specifically in optical metamaterials and metasurfaces. Two algorithms were developed to obtain the electromagnetic (EM) wave response from a metasurface (direct solver) or the metasurface parameters from the EM wave response (inverse solver) for a bi-anisotropic, subwavelength-thick nanostructured film. The algorithm is applied to two different metasurfaces to retrieve their effective homogeneous bi-anisotropic parameters. The effective layer of the same physical thickness is shown to produce the same response to plane wave excitation as the original metasurface.