Schematic of the unit cell of the planar chiral metamaterials under consideration [24]: (a) two relatively rotated layers of four U-SRRs, (b) and (c) two layers of Z-type crosses with φ = 90° and φ = 60°, respectively; the back-layer is the mirror image of the front layer; (d) two relatively rotated layers of cross-wires and (e) design based on two relatively rotated squares. The metal (yellow-color) thickness t_m and the dimensions a_x, a_y, L, w, a, d, φ and s, for each design are presented in Table 1. In Figure 1d grey color corresponds to photoconductive silicon. The wave propagation is along the z direction.