Spectroscopic ellipsometry on photonic crystals made by self-assembled dye-doped P(S/HEMA) nanospheres

In the present work the use of Spectroscopic Ellipsometry (SE) for a direct and non-destructive optical and structural characterization of opaline photonic crystals is demonstrated. The analysis is performed on self-assembled dye-doped polymer nanospheres deposited on glass substrates. We study two different polymers beads: PMMA (as well-known reference material) and poly[styrene-(co-2-hydroxyethyl metacrylate)] [P(S/HEMA)]. We show that SE allows to obtain information about all the most important optical and geometrical features of the photonic structure as the effective refractive index (n(eff)), the refractive index modulation, the optical anisotropy, the air/sphere filling fraction, the layer distance and the size of nanospheres. Results are in very good agreement with those obtained by Scanning Electron Microscope (SEM) analysis and Bragg reflection spectroscopy.