Generating, Enhancing, and Leveraging Nonlinear and Electro-Optic Effects in Silicon-Based Waveguides

In integrated photonics, most fundamental device functionalities rely on nonlinear or electro-optic phenomena, and optical waveguides with higher second- and third-order nonlinear coefficients are generally desirable for high-efficiency modulators and wavemixers. Silicon, despite being a material of interest due to its prevalence in the electronics industry, intrinsically lacks a second-order nonlinear susceptibility, so a great deal of work in the literature has been focused on circumventing this shortcoming by either (1) relying instead on free-carrier plasma dispersion or (2) generating strain-induced second-order effects. This dissertation focuses primarily on providing a comprehensive study of the nonlinear effects in silicon waveguides, with the intent of determining which phenomena and consequent waveguide designs are the most desirable for achieving modulation and wavemixing, respectively. A detailed analysis is additionally applied to the integration of silicon with other media with favorable optical properties, with the goal of designing hybrid waveguides with enhanced nonlinear coefficients. Electro-optic and wavemixing measurements are performed using combination fiber, integrated, and free-space optical setups, and the experimental data show conclusively that conventional silicon waveguide topologies may be modified to improve the performance of modulators and wavemixers in terms of (1) energy efficiency, (2) device footprint, and (3) speed. This work is intended to contribute to the study of nonlinear integrated photonics, ideally advancing the ongoing assimilation of the field by electronics and leading to the eventual design of hybrid photonic-electronic circuits.