Photonic Integrated Circuits for Compact High Resolution Imaging and High Capacity Communication Utilit

"Integrated photonics" refers to the integration of multiple photonic components on a common substrate. Examples of photonic components include waveguides, gratings, couplers, polarizers, interferometers, beam splitters, light sources, and detectors. In turn, these components can then be used as building blocks to realize more complex planar photonic circuits, capable of performing a wide range of functions with applications in optical sensors and communication systems. The development of integrated photonics is the confluence of waveguide technology and photonic disciplines, which deals with the control of light by electrons and vice versa. The optical waveguide technology is the fundamental of integrated photonics which enables light guiding, coupling, splitting, multiplexing and demultiplexing of optical signals.;In the first three chapters of this dissertation, we will discuss the main characteristics of integrated photonics and show relevant aspects of material and fabrication technologies. We will also briefly describe some basic components used in integrated photonics, emphasizing the difference in their design concepts in contrast to conventional bulk optics. Some examples of photonic integrated circuits (PICs) are presented to highlight photonic integration as an elegant solution to realizing multifunctional chip-scale module.;Chapter 4 discusses the arrayed waveguide grating (AWG) as another example of PIC. The AWGs are widely used as optical (de)multiplexers in wavelength division multiplexer (WDM) systems. These devices are capable of multiplexing a large number of wavelength channels into a single optical fiber, thereby increasing the aggregate transmission capacity of the single-mode fiber. We will explain the working principle of AWG devices, and then address several design techniques. Eventually, we will demonstrate a large channel spacing AWG (an 18 channel 3.3 THz channel spacing AWG centered around 1310 nm) and a high channel count AWG (a 512 channel 25 GHz channel spacing AWG centered around 1550 nm).;Chapter 5 investigates the use of PICs in interferometric imaging. In astronomy, optical interferometric imaging is a technique that brings the light of many telescopes together to create images with high angular resolution. While these interferomic telescopes based on PICs achieve the same spatial resolution as the conventional telescopes, they offer much more compact and robust platforms. This chapter further proposes and demonstrates a small-scale interferometric imager based on PIC technology. The PIC interferometer has the potential to become an alternative to conventional telescope interferometer, but with significantly reduced size, weight and power consumption.;Chapter 6 discusses the use of PICs in orbital angular momentum (OAM) communication system. OAM can be understood as characterizing the "twist" of a helical phase front of the light beam. A set of OAM mode forms an orthogonal modal basis set that can be used in a mode-division-multiplexing system, which increases the capacity of optical communication in addition to WDM and polarization division multiplexing (PDM) techniques. This chapter demonstrates the first silicon PIC that is capable of demultiplexing free-space optical beams with multiple OAM states near 1550 nm into the single-mode waveguides. The device is easily connected to high-speed telecommunication components like modulators and photodetectors and is comparable with the CMOS silicon fabrication process.;Chapter 7 summarizes this dissertation and projects possible future research directions.