Hybrid Silicon-Vanadium Dioxide Modulators and Transformation Optics Couplers for Optical Interconnects

Abstract

The ever-growing demand for more powerful computers has led to the emergence of multicore processors. Due to the nature of parallel processing, additional cores significantly improve performance. However, a major roadblock preventing the number of cores from growing without bounds is the rate at which they can share information. Current state-of-the-art technology uses copper electrical interconnects to carry information between cores. Copper interconnects suffer performance deterioration with increased data rates due to cross talk and increased power requirements. Using light to transfer information can help solve these problems leading to more compact and faster interconnects that consume less power. In this dissertation work, two components of optical interconnects based on silicon photonics were investigated: fiber-to-chip couplers and electro-optic modulators. A transformation optics approach was utilized to design a compact and efficient fiber-to-chip coupler. The coupler was experimentally realized on a silicon-on-insulator platform and demonstrated a fivefold improvement in efficiency over a conventional design while occupying very little chip estate. A hybrid VO2-Si material system was used to improve the performance of on-chip silicon electro-optic modulators. The semiconductor-to-metal phase transition of VO2 gives rise to a large change in its dielectric function at ultrashort time scales, which can be harnessed to change the effective index of a propagating mode in hybrid VO2-Si waveguides. Electro-optic switching of hybrid VO2-Si waveguides at ultrafast time scales was demonstrated for the first time along with record values for the electrically triggered VO2 semiconductor-metal and metal-semiconductor phase transition times. A plasmonic electro-optic modulator based on the VO2-Si hybrid material system was also designed and simulated, showing a record high extinction ratio per unit length, ultra-compact footprint, and low threshold power.