title: Doped colloidal photonic crystal structure with refractive index chirping to the [111] crystallographic axis.
abstract: A three-dimensionally ordered array of close-packed colloidal spheres, a photonic crystal structure in which the refractive index of the medium interstitial lattice in a colloidal crystal spatially changes in the [111] crystallographic axis, is demonstrated. The colloidal photonic crystal structure with refractive index chirping was produced by infiltration of a monomer and organic dopants with a high refractive index into a silica opal, followed by interfacial gel polymerization. The resulting photonic crystal structure has a gradually varying stop band at each different (111) plane in the face-centered cubic (fcc) crystal structure at a normal incidence. This novel structure exhibited optical characteristics that have band-gap broadening by the superposition of stop bands at each plane of the crystal with different dielectric functions. Moreover, the refractive index perturbation in the [111] fcc opal also showed a defect state within a pseudo-photonic band gap. This new type of photonic crystal structure should be useful for the band-gap engineering of photonic-band-gap materials.
authors.affiliation: Center for Frontier Materials, Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Buk-Gu, Gwangju 500-712, South Korea.
authors.forename: Jeong-Ho
authors.initials: JH
authors.lastname: Park
authors.forename: Won San
authors.initials: WS
authors.lastname: Choi
authors.forename: Hye Young
authors.initials: HY
authors.lastname: Koo
authors.forename: Jae-Chul
authors.initials: JC
authors.lastname: Hong
authors.forename: Dong-Yu
authors.initials: DY
authors.lastname: Kim