UC San Diego

Electro-optic modulators (EOMs) serve as a technological pillar of the modern telecommunications industry. Without these devices, which convert electrical data into optical data through one of several physical phenomena (depending on the specific technology), telecommunications channels would be severely bandwidth-limited, particularly within data centers. To meet the ever-increasing bandwidth demands of the industry, either more EOMs are necessary (resulting in higher power requirements) or higher bandwidth EOM technology must be developed. This thesis discusses the theory, design, fabrication, and characterization of foundry-compatible hybrid silicon-lithium niobate (Si-LN) electro-optic modulators integrated on a wafer platform, a new technology with potentially far-reaching applications.

By bonding a thin film of ion-sliced LN crystal, which retains the crystal properties of bulk LN, to silicon waveguides in the Mach-Zehnder modulator configuration, it is theoretically possible to exceed the bandwidth limitations of all-Si modulators without abandoning the scalable, dense silicon-on-insulator (SOI) platform. These hybrid devices make use of the favorable linear electro-optic Pockels effect of LN while using the high-index Si waveguide to reduce the optical mode area, so that low-voltage, high-bandwidth devices can be realized. This thesis focuses on developing broadband EOMs with cutoff frequencies beyond 100 GHz. Developing this technology on an SOI wafer platform fabricated via photolithography in a foundry facility presents a realistic path towards next-generation high-speed, low-power integrated EOMs.