The Effects of Disorder on the Optical Spectra of Synthetic Opals

The classification of structural defects of synthetic opals by studying their surfaces using X-ray and optical microscopy is given. Based on the real opal structure, the relative ordering parameter is suggested as a criterion of samples quality. The manifestation of various types of defects in the character of the diffraction pattern of film opals is analyzed. The 1D-photonic crystal model of defective structure considering typical for synthetic opals defects is developed. The reflection spectra by a transfer-matrix method and the density of optical states spectra by a plane wave expansion method are simulated using this model. Comparison of the theoretical and experimental dependencies of relative half-width of Bragg reflection band on relative ordering parameter of the opal structure is given. We show that the best matching between these dependencies occurs when the elastic multiple scattering is taken into account in the model. To study the effects of disorder on spontaneous emission, as well as inelastic scattering the fluorescence spectra of dye R6G and Raman spectra of Bi12SiO20 in synthetic opal are measured. The amplification of both fluorescence intensity of R6G and Raman intensity of Bi12SiO20 in synthetic opal templates is observed.