Fast measurement of photonic stop bands by back focal plane imaging

Back focal plane imaging microscopy of the autofluorescence of a colloidal photonic crystal at fixed wavelength is used to visualize photonic stop bands. Emission angles of up to 74^∘ against the crystals surface normal are detected. Structure and orientation of the crystal lattice, quality of the ordering, and the influence of defects on the optical properties can be probed at high spatial resolution. Exemplary results reveal domains with four-, six- and threefold symmetry, where the latter dominates, as expected for fcc lattices.