A modified Drude-Born-Fedorov model for isotropic chiral media, obtained by finite scale homogenization

Isotropic chiral media can be modelled in several ways. We show that when realizing such a medium from spiral inclusions with real permittivities and permeabilities in a periodic structure, a modified Drude–Born–Fedorov model is obtained. This model equals the original Born model for small wave vectors, but the strength of the chirality depends on the propagation direction. The effective parameters are calculated by an unbiased finite scale homogenization method, which in principle could generate any model.