Non-Hermitian and Non-Linear Dynamics in Integrated Silicon Photonic Resonators

The exponential growth of data-centric computing has imposed fundamental limitations on electronic computing systems, with power dissipation and heat generation emerging as major barriers. At the system level, data movement between memory and processing units now consumes more energy and time than computation itself, a challenge further intensified by the latency and bandwidth constraints of electrical interconnects caused by resistive–capacitive delays and signal integrity issues. At the device level, transistors approaching atomic length scales suffer from increased leakage, variability, and reduced energy efficiency, signaling the physical limits of conventional scaling. In this context, integrated photonics offers a compelling alternative, providing low-loss, high-bandwidth, and low-latency information transport with reduced energy per bit, and enabling scalable parallelism through wavelength-division multiplexing to alleviate the interconnect and power constraints of modern electronic architectures. Motivated by the fundamental power, bandwidth, and data-movement limitations of electronic computing, integrated photonics has emerged not only as an enabling technology for energy-efficient interconnects but also as a platform for realizing new computational and signal-processing paradigms. In particular, the deliberate engineering of loss, coupling, and nonlinearity in photonic systems—traditionally viewed as detrimental—has opened new opportunities through non-Hermitian and nonlinear device physics. In this context, this thesis presents a comprehensive analytical, numerical, and experimental investigation of non-Hermitian and nonlinear photonic devices based on silicon microring resonators and waveguide couplers. Using temporal coupled-mode theory, transfer-matrix methods, and reduced-order models, we develop quantitative frameworks that connect physical coupling mechanisms, intrinsic loss, and nonlinear feedback to experimentally observable spectral and dynamical behavior. These models are validated through systematic characterization of foundry-fabricated devices. First, an optimized 3 ×3 silicon waveguide coupler is designed and experimentally demonstrated as a compact and reconfigurable photon-routing primitive. Full nine-port characterization reveals controlled outer-to-outer crossing, equal three-way splitting, and arbitrary output distributions, with extracted coupling and detuning parameters quantifying fabrication-induced non-idealities. Second, a p-n integrated silicon microring is studied in the non-linear regime, where coupled carrier and thermal dynamics give rise to self-pulsing oscillations. By electrically tuning the free-carrier lifetime via reverse bias, the self-pulsing frequency is widely and rapidly controlled, reaching oscillation frequencies up to ∼190MHz. The thesis then investigates non-Hermitian Taiji microrings and Taiji-based coupled resonator optical waveguides (CROWs), revealing how intentional asymmetry competes with parasitic backscattering to shape spectral response and transport. A reduced coupled mode “hopping” model is introduced to extract practical design rules, demonstrating that robust non-Hermitian operation requires the engineered inter-resonator coupling to exceed roughness-induced backscattering. Finally,a dynamically reconfigurable microring circuit is presented that enables continuous and programmable control of mode coupling. This platform allows on-demand transitions between diabolic points and exceptional points, co herent suppression of backscattering, and electrically tunable optical chirality approaching unity. Together, these results establish experimentally validated device-level frameworks for understanding and controlling asymmetry, loss, non-linearity, and coupling in silicon pho tonic systems. By transforming traditionally parasitic mechanisms into tunable resources, this work advances scalable and reconfigurable non-Hermitian photonic architectures for integrated signal processing, routing, and dynamical control.