Fabrication and characterization of chirped 3D photonic crystals

Two simple methods are developed for fabricating chirped 3D photonic crystals where the stop band position changes continuously or in well-defined steps with position. In the first method, electrically neutral polystyrene beads of various sizes were assembled into a set of ccp regions and each region exhibits a specific stop band whose position mainly determined by the size of the polymer beads. In the second method, highly charged polystyrene beads were organized into an fcc structure whose stop band position changes continuously from approximately 474 to approximately 571 nm over a distance of approximately 6 mm.