Bragg reflection spectroscopy of opal-like photonic crystals

Abstract

We have studied Bragg reflection spectra of photonic crystals based on synthetic opals. The samples under study represented opal-semiconductor composites, in which the opal pores were filled with GaN and GaP, and GaN-inverted structures with the opal matrix removed from the composite. Bragg reflection spectroscopy is found to possess new capabilities for characterization of opal-like structures. A theoretical approach to the reflectance spectrum analysis has been developed on the assumption of a planar spatially periodic medium, accounting for the effects of sintering of $\mathrm{Si}{\mathrm{O}}_{2}$ opal spheres and their uniaxial strain. For an additional characterization of the samples, we considered a structural invariant relating to each other the photonic crystal lattice parameters and the spectral positions of features in multiple Bragg diffraction spectra.