Optical dispersion in synthetic opal matrices filled with europium-oxide-doped silica sols

We have studied typical features in reflection spectra of the (111) surface of opal photonic crystals based on synthetic opals filled with Eu2O3-doped silica sols. The reflection spectrum of the composite of opal and europium-doped silica sols is found to contain a resonance at a wavelength of 617.5 nm. A theory has been developed for describing the optical dispersion of resonant photonic crystals. We have calculated the dispersion curves and reflectivity of undoped and Eu2O3-doped opal crystals and compared the calculated reflection spectra to experimental data. Nanocomposites of opal and europium-doped silica sols can be used in laser cavities.