Integrated Nonlinear Photonics: Theory, Design, and Fabrication

Integrated photonics platform allows miniaturization and dense on-chip integration of diverse optics-based applications ranging from optical communication to machine vision. With significant development in integrated photonics fabrication technology in recent years, low-propagation-loss optical waveguides with sub-wavelength cross-section dimensions are readily available. As nonlinear optical interaction efficiency dramatically scales up with optical wave intensity (power per unit area), the integrated photonics serves as a highly efficient platform for nonlinear optics. Integrated nonlinear photonics – the combination of integrated photonics and nonlinear optics – has enabled various on-chip applications such as all-optical signal processing and generation of frequency combs with efficiency unprecedented in traditional nonlinear optics platforms (bulk nonlinear crystals and optical fibers). In this thesis, we develop an integrated nonlinear photonics system using Aluminum Gallium Arsenide (AlGaAs) on insulator material platform – taking full advantage of the tight waveguide confinement and the high intrinsic nonlinearity of the AlGaAs. A rectangular waveguide is presented with a modal dispersion engineering method, followed by a description of four-wave mixing. Microresonator structure is introduced for further increasing the light intensity utilizing the resonant field enhancement. Several key developments such as thermal tuning and suppression of avoided resonance crossing of the microresonator device are presented. We demonstrate a resonance-enhanced four-wave mixing and Kerr frequency comb generation. A novel near-exceptional-point coupled microresonator system is introduced for longitudinal-mode-selective broadening of resonance enhancement bandwidth.We demonstrate a high-data-rate (up to 38 Gbps) wavelength conversion at a pump power of 1 mW using the coupled microresonator device. Hybrid integration of the AlGaAs and silicon nitride material platform is presented, addressing the need for efficient light transfer between novel nonlinear photonic devices and integrated linear photonic networks. AlGaAsOI fabrication technologies employed for the presented devices are covered. In summary, integrated nonlinear photonics using AlGaAs on insulator material platform is comprehensively investigated from the perspective of theory, design, and fabrication.