Smowton, PeterFwoziah T, Albeladi2025-02-242024https://hdl.handle.net/20.500.14154/74911The aim of this work is to advance the field of Photonic Integrated Circuits (PICs) by designing, fabricating, and characterizing various photonic devices. These devices or functions include an on-chip laser, a fiber-to-chip coupler, an optical resonator, and optical coupling between III-V and Ta2O5 waveguides to enhance photonic integration further. One of the main contributions of this research is the development of an on-chip laser source that employs a Multi-Mode Interference Reflector (MMIR) based on InAs Quantum Dot (QD) lasers. MMIRs have been shown to have advantages over other on-chip mirrors, such as Distributed Bragg Reflectors (DBR), Distributed-Feedback lasers (DFB), and loop mirrors because it is compact and versatile. The results indicate that MMIR lasers outperform traditional Fabry-Perot ridge waveguide (FP-RWG) lasers with two cleaved-facets, demonstrating lower threshold currents, reduced temperature dependency, and higher optical slope efficiency. This makes MMIRs promising candidates for on-chip laser reflectors in integrated photonics. The study also focuses on a low-loss III-V waveguide with a thin high-index AlOx layer to enhance waveguide confinement. It addresses substrate waveguide loss and leads to improved coupling efficiency of GaAs-based Surface Grating Couplers (SGC). Simulation results reveal a significant enhancement in coupling efficiency for a grating with oxidized underlayer compared to unoxidized grating design. The compatibility of high aluminium-containing layers with laser diode epi-layer structures is demonstrated, suggesting the potential of this approach for active-passive integrated platforms. The design and optimization of low-loss Ta2O5 waveguides, which are important for high-quality integrated photonic devices are described. These are expected to be useful to provide non-linear properties although that is not tested within this work, a ring resonator based on Ta2O5 waveguides is designed. The task of connecting and integrating III-V and Ta2O5 waveguides, presenting a hybrid platform with potential applications in compact, energy-efficient, and high-performance photonic circuits, is explored Overall, this research contributes to the evolution of PICs, offering innovative solutions for advanced photonic circuit development.207enQuantum Dot (QD) lasersPhotonic Integrated Circuits (PICs)MMIMulti-Mode Interference Reflector (MMIR)High reflectivityRing resonatorlow-loss waveguideon-chip lasera fiber-to-chip couplerSGCTa2O5 waveguidesAlOx.Thesis