Dimer shape anisotropy: a nonspherical colloidal approach to omnidirectonal photonic band gaps

Theoretical calculations of the photonic band gap forming properties are reported for a class of colloidal dimer-based structures with similarity to zinc blende and which map onto diamond or opalline face-centered cubic structures at the extrema in shape parameters. Inspired by the range of nonspherical building blocks for self-assembly synthesized using seeded emulsion polymerization and sol-gel techniques, we explore in particular the band structures as a function of dimer lobe symmetry and the degree of lobe interpenetration for tangent dimers. Complete photonic band gaps were observed between the second and third, fifth and sixth, or eighth and ninth bands for various shape classes. As well, select inverted and direct dimer-based structures showed two complete band gaps simultaneously.