CHAPTER 4: Tuning Color and Chroma of Opal and Inverse Opal Structures

Photonic crystal materials with stop bands in the visible spectrum produce brilliant structural colors based on Bragg diffraction. Opals and inverse opals are examples of these structurally colored materials that possess periodic arrays of high and low dielectric zones. The nature of these photonic crystals allows for the dynamic tuning of stop‐band position, shape, and intensity, based on changes in lattice parameters and refractive indices of the component materials. This tunability enables opals and inverse opal to be used as optical sensors and pigments whose color changes in response to mechanical stresses, chemical reactions, or solvent infiltration. This chapter summarizes the factors that influence optical stop bands and colors of photonic crystal materials, highlights approaches for dynamic color tuning of both opal and inverse opal photonic crystals, and ends with a discussion on optimization of color in these materials.