Advances in Silicon and Lithium Niobate Photonic Devices for Quantum Applications: Design, Fabrication, and Experimental Studies.

This thesis explores the design, fabrication, and validation of photonic devices on Silicon (Si) and Lithium Niobate on Insulator (LNOI) platforms, addressing critical challenges in advancing integrated photonics for quantum technologies. By leveraging the strengths of both materials, the research develops scalable, high-performance components essential for advancing quantum technologies. On the Si platform, the research focuses on energy-efficient thermo-optic phase shifters and high-efficiency grating couplers for transverse magnetic (TM) modes. A novel undercut design improves thermal isolation, enabling precise phase control with reduced power consumption—critical for scaling quantum systems. Additionally, the Si-based work includes a quantum simulation experiment that models complex spin systems such as spin glasses using photonic circuits. This experiment highlights the potential of Si photonics to tackle quantum phenomena that are difficult to address with classical computing, opening new possibilities in quantum simulation and computation. On the LNOI platform, the focus shifts to addressing the need for high-speed, low-loss optical switches, essential for applications such as demultiplexing quantum dot singlephoton sources and multiplexing nonlinear quantum states. Using the Pockels effect in LNOI, the research develops a high-speed electro-optic switch optimized through advanced fabrication techniques, enabling efficient photon routing with minimal losses. These switches not only maintain quantum state fidelity in communication and computation systems but also support photon storage applications, crucial for future quantum memory and secure communication systems where precision and minimal loss are essential. By combining Si’s scalability for quantum simulations with LNOI’s high-speed switching capabilities, this thesis highlights the complementary strengths of both platforms. Si’s integration with CMOS technology allows for large-scale quantum circuits, while LNOI’s superior electro-optic properties make it highly relevant for efficient, high-speed quantum operations. Together, these advances lay the foundation for next-generation quantum devices, offering practical, scalable solutions for quantum computing, secure communication, and advanced sensing technologies. In conclusion, this research makes significant contributions to the field of integrated quantum photonics. From efficient phase shifters and grating couplers on Si to high-speed switches and photon storage on LNOI, the innovations presented in this work are poised to play a pivotal role in the future development of quantum systems, unlocking new potential in quantum information processing and technology.