Nonlinear optics and characterization of layered and nanostructured materials

Abstract

In Chapter 4, this TDDFT technique is further applied to a filtered database of 2D materials to identify several previously unreported high-intensity nonlinear optical materials. It is found that certain symmetries are highly conducive to strong second harmonic generation. A bond charge model is discussed as a potential heuristic predictor of strong nonlinear optical susceptibility. In Chapter 5, a deeper exploration into more computationally intensive calculations of nonlinear optical properties in TMDs using the TDDFT-BSE method is then presented. The inclusion of spin-orbit coupling (SOC) and its effects on the C-exciton are discussed. The effects of alloying in TMDs with larger unit cells are also explored with the inclusion of excitonic effects. Furthermore, by significantly increasing the smearing in the TDDFT method, which is analogous to lowering the temperature, it is shown that excited excitonic peaks can be resolved in the second harmonic spectrum that agree with experimental reports.