Colloidal photonic crystals

This application is the US national phase of international application PCT/GB00/03405 filed 5 Sep. 2000, which designated the US. A method of growing robust large area colloidal photonic crystals and devices produced thereby. A suspension of monosized colloidal spheres () is subjected to a composite shear () by applying a sequential set of shearing forces. The crystalline layers within the colloid experience shearing forces with components in both x and y directions, forcing the colloid into a singe face-centered-cubic structure in preference to a twinned face-centered-cubic structure. The method may also comprise the use of a dispersion medium which is capable of undergoing a controllable phase change from a liquid phase to a solid phase. The crystal may be fixed into a single face-centered cubic structure.