Far-infrared photonic-plasmonic phase matching enhanced graphene absorption
Date
2019
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Publisher
University of Delaware
Abstract
In this thesis, we investigate a novel device architecture for sensing applications in the far-infrared region. This region is relatively unexplored due to a fundamental problem surrounding the optical spacer which separates the front side planar geometry from the substrate. SiO2 is commonly used but suffers from immense absorptions at wavelengths below 1000 cm-1. To overcome this problem, we use an optically transparent spacer, zinc selenide, which exhibits high transmission well into the far infrared region. We implement a monolayer of graphene that serves to broaden the plasmonic mode and increase the optical absorption through phase and momentum matching of the plasmons. Optimization of the optical spacer thickness, rod length, rod width, and periodicity allow for our device to have plasmonic resonances from 950 cm-1 to below 600 cm-1 with an extinction ratio of more than 28%. This allows for on-chip sensing through geometric tuning. ☐ Photonic crystal waveguides are a fundamental building block for all-optical communications in the chip-scale. By optimizing the radius, lattice constant, and spacing between the photonic crystal arrays, it is possible to place the high-transmission regions or band edge in the wavelength of choosing. The telecommunication bands are the target wavelengths for our project. ☐ This thesis will be broken up into six different chapters. The first four chapters will discuss in detail our graphene modified plasmonic structure starting with a chapter on the introduction to the field of plasmonics, graphene, graphene plasmons, and motivation about current works in the field of graphene-based sensors. The second chapter will discuss design principles and simulations. The third chapter will discuss fabrication and characterization of the device. The fourth chapter will discuss the experimental results. The fifth chapter will briefly discuss our results from the AIM foundry run for our photonic crystal waveguide structures alongside the simulated work and experimental setup. The final chapter will discuss the future directions for both projects.
Description
Keywords
Far-infrared region, Graphene modified plasmonic structure, Photonic crystal waveguide structures