Document Type

Thesis

Degree

Doctor of Philosophy (PhD)

Department

Electrical Engineering

First Advisor's Name

Nezih Pala

First Advisor's Committee Title

committee member

Second Advisor's Name

Sakhrat Khizroev

Second Advisor's Committee Title

committee member

Third Advisor's Name

Irene Calizo

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Yesim Darici

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Ismail Guvenc

Fifth Advisor's Committee Title

committee member

Keywords

Terahertz, Plasmon, Resonant, Circular, split-ring, grating, graphene

Date of Defense

4-4-2017

Abstract

Terahertz (THz) devices are designed to operate from 0.1-10 THz. The THz spectra have unique properties such as penetration through soft materials and reflecting from hard materials, which make THz technologies, a prime candidate for imaging. Plasmons are longitudinal charge oscillations in carrier rich materials. Plasmons can be generated over the channel of transistors inducing a voltage between the source-drain when conditions are satisfied. In this thesis, plasmonic devices operating in the THz region have been studied both theoretically and experimentally investigating GaN/AlGaN and Graphene based transistors.

First, we report on a detailed study of dispersion properties of uniform grating gate THz plasmonic crystals, asymmetric dual grating gate plasmonic crystals and with symmetry-breaking defect-like cavities in order to understand the physics behind THz plasmons. For the first time, we defined the dispersion of plasmons in terms of effective plasmonic index. By adding an additional grating on top of the grating gate with a different periodicity, doubles the amount of absorption. Plasmons can be excited when polarization is perpendicular to the gate. We then showed focusing and exciting of THz plasmons polarization independent using circular grating lenses. Sub-micron THz ring resonators are presented showing THz guiding in plasmonic waveguides.

So far, resonant sensing has been observed only at cryogenic temperatures since electron mobility is high enough at low temperatures to sustain resonant plasmonic excitation at the channel of the detector. Recently, graphene attracted the attention of the researchers because of its high mobility at room temperature. Room temperature detection has been attempted and achieved, however the detectors have very small responsivity with non-resonant behavior since the graphene is sandwiched and fabrication of such detectors in large scale is impossible with the methods used. Here, we present a resonant room temperature detection of THz with upside down free standing graphene FETs having more than a 400 quality factor, a record high number in the field which is up to 50 times higher than GaN detectors and hundreds of responsivity values with a maximum around 400 V/W which is record high for graphene (10,000 times higher than previously reported graphene detector).

Identifier

FIDC001789

ORCID

0000-0003-3595-0631

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Available for download on Wednesday, April 24, 2019

Share

COinS
 

Rights Statement

Rights Statement

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).