A computational investigation into the third-order nonlinear optical properties of cyanine-like polymethines for all-optical switching applications

Abstract

Cyanine-like polymethines have recently attracted renewed attention for their potential as materials to realize all-optical switching applications by demonstrating large real and small imaginary parts of the third-order polarizability at telecommunications wavelengths. In this dissertation, we employ a variety of computational methodologies to investigate the structure-property relationships of promising cyanine-like polymethines. We begin with an overview of the field of nonlinear optics and place cyanine-like polymethines within that context before discussing the remaining challenges confronting their use in all-optical switching devices. We then briefly review the electronic-structure and molecular-dynamics methods used throughout this work. We communicate the main results of this dissertation in Chapters 3 – 6. Chapter 3 focuses on how the interplay between cyanine and counterion steric bulk affects their packing in the bulk. In Chapter 4, we investigate the evolution of the non-covalent interactions between a streptocyanine and counterion as a function of counterion position along the cyanine backbone. Zwitterionic cyanines designed to eliminate the need of an untethered counterion are the focus of Chapter 5, in which we provide design principles. We study the origin of the third-order polarizability of mixed-stack binary charger transfer complexes in Chapter 6. We conclude in Chapter 7 with a synopsis and a look towards future directions.