Three-Dimensional Bi-chiral Photonic Crystals

Four different types of bi-chiral photonic crystals are experimentally realized and characterized (see figure). In these 3D bi-chiral photonic crystals one type of handedness stems from the motif (the spirals in our case) and the other one from the corner, that is, from the fictitious skeleton onto which the motif is arranged. In nature only two of these types of bi-chiral photonic crystals exist. We realized all four bi-chiral combinations for the first time.