Photonic bandgap composites

Abstract

Since the original proposal that three dimensional periodic dielectric structures could exhibit a photonic bandgap, considerable attention has been focused on developing these materials into a form which is suitable for use in photonic applications. Unfortunately, the general exploitation of visible photonic crystals as devices has been hindered by the difficulties in creating 3-D periodic dielectric structures with a feature size comparable to the wavelength of visible light. Though a number of groups have made progress applying conventional microlithographic techniques to this end, this objective remains a challenge employing these techniques. Focus has now turned to systems which undergo self organization at a nanometer length scale, such as colloidal crystals. Systems exhibiting self-assembly characteristics hold promise as a practical route to generating photonic crystals. A self-assembly approach to generating photonic crystals has emerged which involves the longe range electrostatic repulsive interactions of suspended colloidal spheres bearing a high surface charge and arranged in ordered arrays. These crystalline colloidal arrays (CCA) are three dimensionally ordered lattices of self-assemble monodisperse polymer colloidal particles, dispersed in a liquid media. At high particle concentrations, long-range electrostatic interactions between particles result in a significant inter-particle repulsion which yields the adoption of a minimum energy colloidal crystal structure with either bcc or fcc symmetry and spatial periodicities that range from ca. 100-1000 nm