UC Davis

Photonic integrated circuits (PICs) are widely used in various applications, such as optical sensing, computing, and communication, thanks to the development of multiple photonic components, including light sources, waveguides, couplers, splitters, combiners, multiplexers, detectors, and modulators. Many material platforms can be employed for PICs. Silicon photonics taking advantage of the mature complementary metal-oxide-semiconductor (CMOS) fabrication technology stands out as a good choice. Silicon-on-insulator (SOI) platform is attracting more interest since it is CMOS compatible, cheap, and scalable. Silicon nitride (Si3N4) platform is also CMOS compatible and can be a supplementary and substitution of the Si platform in some cases, especially when low propagation and high scalability are required. Complex integrated photonics systems usually require the integration of many platforms.The explosive growth of the demands for sensing and data transferring drives the development of integrated photonics. For example, future autonomous vehicles require low-cost, high-performance light detection and ranging (LIDAR) systems. Optical interconnects are proposed and being explored for modern high-performance computing (HPC) systems. Modern astronomy needs a small size, weight, and power consumption optical sensing system to significantly reduce the cost. Integrated photonics are continuously being explored and developed for higher performance and lower cost. This dissertation presents the development of PICs for optical imaging and communication. Chapter 1 introduces integrated photonics and briefly introduces all the works in this dissertation. Chapter 2 presents our multi-layer Si3N4 platform, including the device design, simulation, fabrication, and measurement. This chapter experimentally demonstrates our multi-layer Si3N4 platform. Chapter 3 proposed and demonstrated a low-loss and broadband optical interposer for large-scale integration. The interposer includes low-loss inter-chip couplers and can be extended to a wafer scale, which shows great potential for large-scale heterogeneous integration for modern sensing and communication systems. Chapters 4 and 5 discuss the segmented planar imaging detector for electro-optic reconnaissance (SPIDER) realized by PICs for astronomy. The SPIDER uses interferometric imaging based on PICs and can significantly reduce the size, weight, and power consumption compared to traditional bulk optical devices. Chapter 4 presents a SPIDER imager formed by many chips and a high-resolution SPIDER imaging achieved using a wafer-scale fabrication technique. Chapter 5 presents a surface-coupled SPIDER imager based on a broadband surface coupler. Chapter 6 investigates the PICs for an elastic RF-optical network. The PICs are based on our multi-layer Si3N4 platform and include arrayed waveguide grating (AWG), multi-mode interferometer (MMI), and thermal phase shifters. The PICs show the capability of generating optical signals for RF-beam forming. Chapter 7 summarizes the dissertation.