Features of the manifestation of a stop band in the spectrum of light diffracted at a glass-opal interface

The diffraction of light passing through a glass plate coated by an artificial opal film has been analyzed. It has been shown that the stop band of a photonic crystal is manifested against the background of the unchanged spectrum of reflected and refracted Bragg waves. The position of this stop band can be changed under a small change in the concentration of a number of substances filling the photonic crystal. The application of such an optical system as an optical chemical sensor has been demonstrated.