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(Color online) (a) Core/shell architecture of precursor particles (top), self-assembled into polymer opals (below). The relative orientations of the  lattice plane and the shear-processing direction are shown. (b) Schematic of experimental goniometer, with angles of incidence (θ) and detection (φ) relative to sample normal as indicated.
(Color online) (a) Normal incidence bright-field reflectance spectra for a series of red opal films with increasing refractive index contrast. These samples were doped with 0.05 wt. % of carbon. (b) Reflectance spectra based on a corresponding 1D multilayer model, with parameters λpeak = 600 nm, 100 layer-pairs, γ = 15 nm and α = 8.9 × 103 m−1. (c) Reflectance peak heights plotted vs. index contrast, Δn, with linear fits.
(Color online) (a) Scattered light spectra for representative Δn = 0.15 sample, (b) transformed into k-space as projected onto the k z−k x plane. The reciprocal lattice vector g 111 is at kz = 32 μm−1. (c) Peak scattering intensity as a function of angular deviation, δ, relative to the specular-reflectance direction (−θ). (d) Maximum scattering intensity and FWHM of scattering cones for θ = 30° and 45°. For clarity, the index contrast is displayed on a logarithmic axis.
Characteristic parameters of samples; average refractive-index (nav ) from refractometry, calculated Δn, mean particle size from hydrodynamic chromatography, and measured normal incidence Bragg wavelength (λ111). See Ref. 9 for further details.
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