| Recent developments in photonic integrated circuits (PICs) are attracting strong interest for their advances in building scalable, high-throughput, and low-cost on-chip optical communication systems. The silicon-on-insulator (SOI) platform is compatible with CMOS technologies which allow for optic-electronic interconnects in the future photonic-electronic integration. In the meantime, Silicon nitride (Si3N4) based PIC platforms are becoming outstanding solutions because of their relatively low optical propagation losses on a silicon CMOS compatible platform. The multilayer structure is promising for future low-loss, small-footprint, and high-density 3D PICs. The key components in this field including arrayed waveguide gratings/routers (AWG/AWGR), optical modulators, and germanium photo-detectors are forming the path to the on-chip passive optical circuits. Heterogeneous integration opens an access to realizing the integration of active components on silicon substrates as light sources of the on-chip optical systems. In addition, heterogeneous integration of various materials is adding powerful functions to the silicon photonic platform, such as the athermalization and the magneto-optical effect.;This dissertation pursues the development of 2D passive photonic devices as well as 3D multilayer photonic devices, integration of III-V materials on silicon substrates, and novel materials integration on the silicon photonic platform. The investigated2D passive photonic devices include the cascaded multimode interference (MMI)couplers, the uniform splitting star couplers, the low-loss arrayed waveguide gratings/routers (AWGs/AWGRs), and the uniform emission gratings. Heavy emphasis is the silicon nitride (Si3N 4) multilayer platform and the 3D photonic devices, including the vertical Y-junctions and the 3D couplers with arbitrary power splitting ratio. Along with passive photonic device demonstrations, the demand of more useful platforms leads the path to heterogeneous integration. To realize the integration of functional materials on silicon substrates, we investigated direct wafer bonding and RF magnetron sputtering in this dissertation. By using the wafer bonding approach, we demonstrated the AlGaAs/GaAs multiple quantum wells (MQWs) thin film integration on silicon substrates. By using the RF magnetron sputtering approach, we demonstrated the integration of novel materials on the silicon photonic platform, such as titanium dioxide (TiO2) for athermal applications, and bismuth-iron-garnet (BIG) for magneto-optic isolators. |
