Optical properties of gyroid structured materials : from photonic crystals to metamaterials

The gyroid is a continuous and triply periodic cubic morphology which possesses a constant mean curvature surface across a range of volumetric fill fractions. Found in a variety of natural and synthetic systems which form through self-assembly, from butterfly wing scales to block copolymers, the gyroid also exhibits an inherent chirality not observed in any other similar morphologies. These unique geometrical properties impart to gyroid structured materials a host of interesting optical properties. Depending on the length scale on which the constituent materials are organised, these properties arise from starkly different physical mechanisms (such as a complete photonic bandgap for photonic crystals and a greatly depressed plasma frequency for optical metamaterials). This article reviews the theoretical predictions and experimental observations of the optical properties of two fundamental classes of gyroid structured materials: photonic crystals (wavelength scale) and metamaterials (sub-wavelength scale). Gyroids are chiral minimal surface morphologies which are found in a variety of natural and synthetic systems, ranging from butterfly wing scales to self-assembled block copolymers. The optical properties of gyroid structured materials are reviewed here on two fundamental length scales, which behave as either photonic crystals or optical metamaterials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim