Photonic crystals of core-shell colloidal particles

We report on the fabrication and optical transmission studies of thin three-dimensional photonic crystals of high-dielectric ZnS-core and low-dielectric SiO2-shell colloidal particles. These samples were fabricated using a vertical controlled drying method. The spectral position and width of a stopgap depend on the core-to-shell ratio, in a manner consistent with numerical calculations. Both experiments and calculations show that the relative L-stopgap width in the case of high-index core low-index shell particles can be larger in comparison to the case of homogeneous particles of either material. The core-shell morphology gives additional control over the photonic stopgap characteristics.