Keywords
Metamaterials, Thermochromic, Thin Films
Abstract
Metamaterials are engineered periodic composites that have unique refractive-index characteristics not available in natural materials. They have been demonstrated over a large portion of the electromagnetic spectrum, from visible to radiofrequency. For applications in the infrared, the structure of metamaterials is generally defined using electron-beam lithography. At these frequencies, the loss and dispersion of any metal included in the composite are of particular significance. In this regard, we investigate deviations from the Drude model due to the anomalous skin effect. For comparison with theoretical predictions, the optical properties of several different metals are measured, both at room temperature and at 4 K. We extend this analysis to the coupling between plasmon and phonon modes in a metamaterial, demonstrating that very thin oxide layers residing at the metal-substrate interface will significantly affect the spectral location of the overall resonance. Oxide-thickness-dependent trends are then explored in some detail. Potential applications of this general area of study include surface-enhanced infrared spectroscopy for chemical sensing, and development of narrowband notch filters in the very long wavelength infrared. We then consider various possibilities for development of tunable infrared metamaterials. These would have wide applicability in dynamically variable reflectance surfaces and in beam steering. We consider several methods that have been previously shown to produce tunable metamaterials in the radio frequency band, and explore the challenges that occur when such techniques are attempted at infrared frequencies. A significant advance in tunable-infrared-metamaterial technology is then demonstrated with the use of thermochromic vanadium dioxide thin films. Highlights include the first demonstration of a tunable reflectarray in the infrared for active modulation of reflected phase, the first demonstration of a tunable resonance frequency in the thermal infrared band, and the largest resonance-frequency shift recorded to date in any part of the infrared. Finally, future work is proposed that holds the promise of wideband frequency tuning and electronically-controllable metamaterials.
Notes
If this is your thesis or dissertation, and want to learn how to access it or for more information about readership statistics, contact us at STARS@ucf.edu
Graduation Date
2010
Advisor
Boreman, Glenn
Degree
Doctor of Philosophy (Ph.D.)
College
College of Engineering and Computer Science
Department
Mechanical, Materials, and Aerospace Engineering
Degree Program
Materials Science and Engineering
Format
application/pdf
Identifier
CFE0003201
URL
http://purl.fcla.edu/fcla/etd/CFE0003201
Language
English
Release Date
August 2010
Length of Campus-only Access
None
Access Status
Doctoral Dissertation (Open Access)
STARS Citation
Shelton, David, "Tunable Infrared Metamaterials" (2010). Electronic Theses and Dissertations. 4269.
https://stars.library.ucf.edu/etd/4269