Local Structure and Shaping of Ferroelectric Domain Walls for Photonic Applications
Open Access
- Author:
- Scrymgeour, David A
- Graduate Program:
- Materials
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 08, 2004
- Committee Members:
- Venkatraman Gopalan, Committee Chair/Co-Chair
Evangelos Manias, Committee Member
Susan E Trolier Mckinstry, Committee Member
Kenji Uchino, Committee Member - Keywords:
- piezoelectric force microscopy
optical devices
lithium tantalate
lithium niobate
ferroelectrics
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QPM - Abstract:
- Ferroelectric lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) have emerged as key technological materials for use in photonic applications, due to the high quality of crystal growth, optical transparency over a wide frequency range (240nm – 4.5 um), and their large electro-optic and nonlinear optical coefficients. Emerging fields of optical communications, optical data storage, displays, biomedical devices, sensing, and defense applications will all rely heavily on such ferroelectrics as a versatile solid-state photonic platform. Diverse functionalities can be created in these materials simply through the patterning of the ferroelectric domains. By creating specific domain features in these materials, it is possible to create new laser wavelengths from existing sources as well as active electro-optic structures that can dynamically focus, shape and steer light. However, the process of domain shaping today is mostly empirical, based on trial-and-error rather than sound, predictive science. The central focus of this thesis work is to develop a fundamental understanding of how to shape and control domain walls in ferroelectrics, specifically in lithium niobate and lithium tantalate, for photonic applications. An understanding of the domain wall phenomena is being approached at two levels: the macroscale and the nanoscale. On the macroscale, different electric field poling techniques are developed and used to create domain shapes of arbitrary orientation. A theoretical framework based on Ginzburg-Landau-Devonshire theory is developed to determine the preferred domain wall shapes. Differences in the poling characteristics and domain wall shapes between the two materials as well as differences in material composition relates to nonstoichiometric defects in the crystal. At the nanoscale, these defects influence the local electromechanical properties of the domain wall. Understanding from both of these approaches has been used to design and create photonic devices through micro-patterned ferroelectrics. Increased fundamental understanding of the poling kinetics and domain wall properties developed in this thesis can lead to a more predictive, scientific towards domain wall shaping.