Simple model for dielectric thin-film helicoidal bianisotropic media

A simple model to predict the effective properties of a porous, dielectric, thin-film helicoidal bianisotropic medium (TFHBM) is presented. A local permittivity dyadic is obtained, assuming that the TFHBM is made of electrically minute needles with a certain shape factor; and thus the TFHBM is locally homogenized into a nonhomogeneous continuum. The determination of the shape factor by comparison with measurements of the optical rotation spectrum is examined in detail, and relationships between structural and other variables are extracted from the predictions of the model. These preliminary results point out the need for more and careful optical experiments on TFHBM slabs to fabricate better theoretical models.