Visible and near-infrared silica colloidal crystals and photonic gaps

The transmission spectra at the high-symmetry points of the first Brillouin zone are measured for three face-centered-cubic colloidal crystals made of silica spheres of different submicrometer sizes. It is found that at the $U$ point the transmission dip exists not only for an $s$ wave, but also for a $p$ wave. Moreover, at the $W$ point the transmission dips of both $s$ and $p$ waves appear at the same wavelength. Our calculations confirm that these dips correspond to the lowest band gaps of the high-symmetry points. The structures and parameters of these crystals are determined by the Kossel-rings analysis as well as by the transmission spectra.