Selective control of light beams in diffraction experiments on synthetic opals

Abstract

This paper reports on an experimental and theoretical investigations of the possibility of selectively controlling the intensity of {hkl} diffraction reflections in synthetic opals. The calculations of the photonic stop-band width for low-contrast multi-component photonic crystals argue for a selective pattern of the vanishing of various {hkl} stop bands (and, accordingly, of the various {hkl} diffraction reflections) under variation of the dielectric permittivity of one of the components. Optical diffraction patterns have been studied visually and recorded in various scattering geometries with bulk opal samples illuminated by white unpolarized light. The experiments have made use of immersion spectroscopy, a method reducing essentially to successive measurements of diffraction patterns under variation of the dielectric permittivity of the liquid filler of the opal matrix. The {111} and {220} Bragg reflections have been observed to weaken noticeably at the filler permittivities matching very well with the values derived earlier from an analysis of transmission spectra.