Chiral Material With Tunable Double Plates

A double slab with chiral structures based on three-segment cranks is analyzed for linearly polarized and normal incident waves. Both slabs are equal and are constituted by a two-dimensional lattice of four same-handedness metallic cranks. The slabs are parallel, with the unit cells perfectly aligned, and each layer is built on a standard FR4 board. Using a free-wave experimental setup and numerical simulations, the transmission and reflection coefficients were determined under normal incidence of linearly polarized waves. The retrieved values for the rotation angle, chirality parameter, refractive index, and ellipticity show a clear chiral behavior for a spacing lower than the slab width. It has also found that as the distance between the two layers increases, the resonant frequency also increases, and this dependence is close to exponential. Based on these observations, a system composed of two chiral slabs can be used as a tunable rotator or a polarization filter.