Date of Award

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

Committee Chair

Robert Lindquist

Committee Member

Junpeng Guo

Committee Member

Laurie L. Joiner

Committee Member

Patrick J. Reardon

Committee Member

Mark Tillman

Subject(s)

Terahertz technology., Metamaterials.

Abstract

In recent years, the terahertz (THz) band of the electromagnetic spectrum has received considerable attention. The THz region falls above the RF (radio frequency- gigahertz frequencies) engineering and falls below IR (infrared frequencies). The region has been referred to as the terahertz gap because it has been highly underutilized in spite of the fact that THz waves have unique properties that provide advantages in medical and defense applications. The increase in THz research has been a result of the significant advances in THz sources and detectors. To continue the advancement of THz technology, component research that can actively manage the THz beam in amplitude, phase, and polarization is critical. In this dissertation, a longitudinally stratified metamaterial structure using liquid crystals was developed, simulated, fabricated, and tested as a platform to realize THz components. To realize such platform, the work conducted in this research had several impactful accomplishments to overcome the many challenges to build practical components that work in the THz. First, the utilization of the longitudinal stratified metamaterial structures as tunable platform in Thz frequencies enable reasonable response times (ms) and low voltages (<15 V). Second, the incorporation of frequency selective surfaces (FSS) as transparent electrode enabled to date the highest ever measured transparency (93.4%) in the THz regime for polarization independent electrode while maintain electric field uniformity. Third, the development of the microfabrication processed to build tunable components on both quartz and Teflon substrate. This accomplishment opens the opportunity to develop component that requires flexible or curved structures. Finally, the simulation code for the modeling based on the concept of stratified metamaterial structure was developed to design materials that do not exist in nature. An artificial chiral media in THz region was modeled using twisted structure analogous to the cholesteric LC in the optical region. Overall, the research has provided a practical platform to develop future tunable components in the THz region.

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