Doctor of Philosophy (Ph.D.), University of Dayton, 2025, Electrical Engineering

The Electro-Optical (EO) effect refers to the change in the optical properties of a material in response to a slowly varying external electric field compared to optical frequencies. This effect is key in EO modulators and beam steerers, which utilize the medium's linear or quadratic EO effect to modulate or steer light. A traveling-wave Mach-Zehnder modulator (TW-MZM) is used in optical communications for rapid and efficient light modulation, with a longer interaction region ideal for high-speed applications compared to lumped-element versions. On the other hand, the EO beam steerers use either an optical phased array (OPA) based on an EO thin film or a bulk EO crystal. Despite advantages like speed, robustness, and compactness, the EO steerers have limited angles, apertures, and high production costs. OPAs also struggle with low diffraction efficiency and dispersion, while bulk crystals are crystal polarization-dependent and require high voltages. To overcome or mitigate some of those drawbacks, this dissertation aims to tackle the following five key questions that have remained unresolved in the field of EO beam steerers for decades. How can bulk EO crystals be used for fast deformable mirrors, various types of varifocal lenses, and nonmechanically steer a large aperture light to a wide angle? How to increase the efficiency of OPAs and overcome the dispersion? How to make the OPAs manufacturable due to the very large number of electrodes? How to steer a large aperture continuously to a wide angle with OPAs? How can light be steered in a mechanical and non-mechanical hybrid manner to direct it mechanically and scan within a small area non-mechanically, or to perform back scanning non-mechanically? This approach is particularly relevant in space applications, where back scanning may be important to account for delays caused by the speed of light. The first section of the research provides a detailed exploration of a bulk SBN75 single crystal - known for (open full item for complete abstract)

Committee: Paul McManamon (Advisor); Jonathan Slagle (Committee Member); Eric Balster (Committee Member); Andrew Sarangan (Committee Member) Subjects: Electrical Engineering; Engineering; Optics; Physics