Bragg diffraction of light as a powerful tool in the study of photonic crystals

We suggest a new approach to the study of photonic crystals, based on direct visualisation of the photonic bandgap structure from Bragg diffraction patterns. Using high quality synthetic opals as photonic crystals, we have demonstrated how the Bragg diffraction of light can provide observation and analysis of the photonic band gap structure. We observed directly and photographed Bragg diffraction patterns as symmetrical sets of color spots on a screen, which appeared, displaced and disappeared, as the crystal was rotated relative to the incident laser beam. The diffraction patterns were observed under laser illumination with different wavelengths. The analysis of the experimental data can provide the number and orientation of the crystallographic planes responsible for the Bragg diffraction, as well as information about disorder in opal structure.