Optical properties and diffraction effects in opal photonic crystals

Il lavoro contiene una formulazione teorica che permette di calcolare le proprietà ottiche di cristalli fotonici tridimensionali quali gli opali artificiali, con varie applicazioni.

Abstract: Optical properties of fcc opals oriented along the [111]direction are calculated by means of a scatteringmatrix approach based on approximating each sphere with cylindrical slices. The use of a plane-wave basis in
each layer allows distinguishing zero-order reflection and transmission from higher-order diffraction spectra.
Optical spectra at large values of the angle of incidence indicate the presence of diffraction effects and of
polarization mixing along the LW orientation. Reflectance and transmittance in the high-energy region show a rich spectral dependence and compare reasonably well with recent experimental observations on polystyrene opals. Diffraction spectra as a function of the number of layers display an oscillatory behavior, pointing to the existence of a Pendellösung phenomenon, related to the exchange of energy between two propagating modes in the investigated three-dimensional photonic crystal. This phenomenon could be observed in transmittance experiments on high-quality opals with controlled thickness.