Dissertation Defense: Tengfei Li

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Title: Enhancement of Optical Properties in Artificial Metal-Dielectric Structures

Abstract: The electromagnetic properties of materials, crucial to the operation of all electronic and optical devices, are determined by their permittivity and permeability. Thus, behavior of electromagnetic fields and currents can be controlled by manipulating permittivity and permeability. However, in the natural materials these properties cannot be changed easily. To achieve a wide range of (dielectric) permittivity and (magnetic) permeability, artificial materials with unusual properties have been introduced. This body of research represents a number of novel artificial structures with unusually attractive optical properties. We studied and achieved a series of new artificial structures with novel optical properties. The first one is the so-called hyperbolic metamaterials (HMMs), which are capable of supporting the waves with a very large k-vector and thus carry promises of large enhancement of spontaneous emission and high resolution imaging. We put these assumptions to rigorous test and show that the enhancement and resolution are severely limited by a number of factors. (Chapter 2 and 3). Then we analyzed and compared different mechanisms of achieving strong field enhancement in Mid-Infrared region of spectrum based on different metamaterials and structures. (Chapter 4). Through design and lab fabrication, we realized a planar metamaterials (metasurfaces) with the ability to modulate light reflection and absorption at the designated wavelength. (Chapter 5). Based on an origami-inspired self-folding approach, we reversibly transformed 2D MoS2 into functional 3D optoelectronic devices, which show enhanced light interaction and are capable of angle-resolved photodetection. (Chapter 6). Finally, to replace the conventional magnetic based optical isolators, we achieved two novel non-magnetic isolating schemes based on nonlinear frequency conversion in waveguides and four-wave mixing in semiconductor optical amplifiers. (Chapter 7).

Committee Members:

Jacob Khurgin, Department of Electrical and Computer Engineering

Amy Foster, Department of Electrical and Computer Engineering

David Gracias, Department of Chemical and Biomolecular Engineering

Susanna Thon, Department of Electrical and Computer Engineering

 

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