Electro-optic modulators in silicon photonics using silicon-organic hybrid materials

Photonic integrated circuits (PICs) have emerged as a promising platform for telecommunications, chip-scale interconnects, sensing, and quantum computing. Continued progress depends on improvements in core building blocks such as modulators, switches, and reconfigurable photonic components. However, due to the centrosymmetric nature of silicon, silicon-only devices rely on carrier-based phase-shift mechanisms---including thermo-optic and free-carrier effects---which impose trade-offs in speed, power consumption, loss, and footprint. In contrast, the Pockels effect enables carrier-free phase modulation with low power consumption, high efficiency, and broad intrinsic bandwidth, making it highly attractive for next-generation PICs. While inorganic materials such as lithium niobate and barium titanate have demonstrated strong Pockels responses, organic electro-optic (EO) materials---particularly EO polymers (EOPs)---offer competitive performance and compatibility with silicon platforms. Silicon--organic hybrid (SOH) systems therefore provide a compelling route toward high-speed, low-power, and reconfigurable photonic devices. However, challenges including scalable poling, void-free infiltration, and reproducible nanostructures remain key barriers to integration. Conversely, liquid crystals provide strong phase shifting but are typically limited by slow switching speeds, restricting their use in high-speed applications. This dissertation addresses these limitations through device engineering and material innovation. Charge-barrier layers are investigated to enhance poling efficiency in slot-waveguide modulators by suppressing leakage current. For a 40 nm slot waveguide, a balanced Mach--Zehnder modulator (MZM) achieves Vpi.L approximately 1.19 V.mm, with simulations indicating potential reduction to ~0.35 V.mm and electro-optic bandwidths beyond approximately 28.5 GHz. In parallel, engineered light--matter-interaction nanostructures, including the finger-loaded strip waveguide, are proposed, simulated, and experimentally demonstrated. This work also introduces a poling-free SOH platform through the first demonstration of the Pockels effect in ferroelectric nematic liquid crystals (FN-LCs), which exhibit a GHz-fast phase-shift mechanism. The first FN-LC ring modulator is demonstrated, achieving high bandwidth, large detuning efficiency, and low static power consumption. A total of 108 FN-LC--on--Si modulators were fabricated using in-house and foundry processes, with selected devices integrated via photonic wire bonding. Finally, analytical frameworks are developed to evaluate modulation efficiency, linearity, and gain, with a three-arm hybrid MZM projected to achieve approximately 15.5 dB gain and approximately 141 dB linearity.