Emerging Optical Properties From the Combination of Simple Optical Effects

Abstract

This thesis explores the intersection of materials science and optics that is colored materials. Traditionally, this field has been limited to structurally colored materials; however, with the advent of plasmonic nanoparticles with designed absorptivities and metamaterials, there has been an increase in the number of fabrication methodologies for colored materials which has also led to the discovery of new types of colored materials that would not typically be considered to be structurally colored. With this expansion, researchers in the field of structural color are creating hybrid materials that rely on both the nanoscale morphology of structurally colored materials and the addition of absorption to these materials which causes a host of different effects. This thesis will first give an overview of a type of classical structural color research that is still very active--self assembled structurally colored materials. Chapter 1 presents a brief review of the field, focusing on colloidal structures and the optical properties obtainable by utilizing different materials, geometries, and additives with colloidal self-assembly. Chapters 2 and 3 present specific examples of these types of structurally colored materials. Chapter two focuses on photonic balls made of spherically assembled colloidal particles. Chapter 3 presents a lithographic method for adding hierarchy to a surface-assembled colloidal photonic crystal. This hierarchy hints at the ability to create novel, combination optical effects by superposing two structural color geometries. Chapter 4 expands on this idea of combining optical effects with a review on the recent trend in the field of colored materials with the combination of hierarchical structures, the addition of absorption into structurally colored materials, and the addition of plasmonic materials into these structures to create many new types of materials and color effects. Chapter 5 gives an example of the former type of material, wherein two structural color geometries (in this case, a diffraction grating and an orthogonally oriented diffraction grating) are superposed to give a composite optical effect. Chapter 6 gives an example of the addition of absorption into a structurally colored material to generate something more complicated than just the combination of different geometries, wherein the complex refractive index of the material changes the boundary conditions for the accumulated phase in the structure.