The schematic of the chiral resonator that composes chiral metamaterials, with the unit cell shown on the right. The square two-gap asymmetric split ring resonator (ASRR) with geometric parameters as follows: a = 60 μm, d = 10 μm, w = 6 μm, g = 3 μm. (a) The single-layer chiral metamaterial. (b) The symmetric bilayer metamaterial (SBM). (c) The asymmetric bilayer metamaterial (ASBM).