Publication Date
2009
Document Type
Thesis
Committee Members
Jerry Clark (Committee Member), Jason Deibel (Committee Member), Lew Yan Voon Lok (Other), Doug Petkie (Committee Chair)
Degree Name
Master of Science (MS)
Abstract
Sub-mm wave technology (also known as Terahertz/THz) is a rapidly developing field of electro-optics which has great potential in a variety of applications. Generally defined as the band of the electro-magnetic spectrum with frequencies spanning from 300 GHz to 30 THz, sub-mm waves are non-ionizing and are capable of passing through a wide range of dielectric substances making them well suited for imaging purposes such as non-destructive materials evaluation (NDE). Because of their high sensitivity to metals and ability to penetrate surface obscurants such as paint, oil, and epoxy sub-mm waves are capable of imaging corrosion damage on metallic surfaces as well as burn damage in composites routinely used in aerospace structures, with resolution comparable to many of the currently employed NDE techniques. In order to avoid failure of components during operation, many aircraft parts are replaced earlier than necessary leading to higher costs that could be reduced if the degree of damage in the component material could be determined non-destructively without requiring contact with the section to be imaged, thus a portable real-time sub-mm wave imaging system if developed would posses significant promise in the NDE market. We have developed a sub-mm wave imaging system and have compiled a library of images which successfully demonstrate the potential of such a system in evaluating aerospace materials. However there are still many unsolved issues related to the propagation of sub-mm wave radiation that need to be addressed before a practical system can be produced for use in the field. One major problem is that all of the substances which posses the refractive index profile and absorption coefficients necessary for the production of a sub-mm waveguide equivalent to fiber-optic cables are crystalline, making them impractical for use in NDE applications. Since the sub-mm wave imaging systems we have researched are active a practical NDE system would either need a compact source or a method of propagating sub-mm radiation over substantial distances to the sample to be imaged. One proposed method is the utilization of what are known as Sommerfield-Zenneck waves, or surface plasmon polaritons (SPPs). These surface electron density waves are capable of propagating over large distances and many metals posses SPP modes with frequencies in the sub-mm wave band. In addition to our NDE efforts, we have constructed a wire waveguide capable of exciting and transmitting these modes, and have characterized a number of its properties via imaging of the diffracted outgoing wave.
Page Count
58
Department or Program
Department of Physics
Year Degree Awarded
2009
Copyright
Copyright 2009, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.
