Micro and Nano Engineering Enabled GaAs Photoconductive Semiconductive Switches and KTN Crystal based EO Devices
Restricted (Penn State Only)
- Author:
- Liu, Ruijia
- Graduate Program:
- Electrical Engineering (PHD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 04, 2023
- Committee Members:
- Madhavan Swaminathan, Program Head/Chair
Osama Awadelkarim, Outside Unit & Field Member
Julio Urbina, Major Field Member
Victor Pasko, Major Field Member
Shizhuo Yin, Chair & Dissertation Advisor - Keywords:
- electro-optics
photoconductive semiconductor switches
nanotechnology
opto-electronics
solid-state - Abstract:
- This dissertation discusses new developments in the research and application of both Nano-engineered photoconductive semiconductor switches (PCSS) based on gallium arsenide (GaAs) and solid-state electro-optics devices based on potassium tantalite niobate (KTN) single crystals. A new method for improving the trigger performance of GaAs PCSS was achieved through a sub-wavelength nano wall array fabricated in between switching electrodes. Through this method, light utilization efficiency was increased. Consequently, key performance factors of PCSS such as required trigger fluence, trigger intensity and on-state resistance in both linear and non-linear operating modes have all been improved. The lock-on time in nonlinear mode was 10x longer compared to the device without the structure. This work has paved the way toward a faster dynamic response for systems that utilize PCSS. This work showcases the first set of complete pattern transfer techniques on KTN crystals. These techniques include electron beam lithography, direct laser writing, and deep inductively coupled plasma (ICP) etching. This breakthrough paves the way for more sophisticated applications and experiments with KTN-based devices. Leveraging these advancements, we have successfully designed and tested an electrode surface topologically enhanced KTN deflector. Our systematic study reveals an increased deflection range, achieved without the need for applying higher voltages. This enhancement addresses the dielectric heating issue prevalent in high-frequency applications, such as optical coherence tomography (OCT) and high-speed LiDAR. The newly developed technical route for KTN nano-fabrication has led to the creation of the first KTN-based diffraction grating and nano-ridge waveguide. This KTN grating demonstrates potential for application in electrically tunable lasers, which possess high damage thresholds, and in spectrometers, which highlights its versatility and significance. Our research also includes the experimental study of a two-dimensional (2-D) KTN scanning system that incorporates surface modifications and ultraviolet (UV) illumination. This system, operating on the principles of electrical field and light control, retains the fast-scanning characteristics of the conventional KTN 1-D deflector while introducing the capability for 2-D scanning. Based on these recent advancements, we propose the development of KTN-based metasurfaces and micro-resonators, along with the implementation of Mach-Zehnder Interferometer (MZI) electro-optic modulators created via femtosecond laser-induced KTN waveguides. These innovations promise to further expand the capabilities and applications of KTN in the field of integrated photonics circuits.