Photonic band structure of bcc colloidal crystals

Abstract

Self-ordering colloidal systems are being recognized as possible candidates for optical photonic crystals. Such structures exhibit three-dimensional periodicity in refractive index, and possess lattice dimensions comparable to optical wavelengths. Recently, fcc colloidal crystals of water-suspended polystyrene microspheres were investigated in the context of photonic band structure. At lower polystyrene volume fractions, these colloidal suspensions crystallize in the bcc crystal lattice. This work extends our investigation of this system to cover the bcc phase and reiterates the use of Kossel lines in mapping the underlying photonic band structure. Along certain crystal directions, numerous Kossel lines intersect, giving rise to unusually large optical stop bands.