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Nonlinear Optical Properties and Fiber-Laser-Based Applications of Transition Metal Dichalcogenide Monolayers.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Nonlinear Optical Properties and Fiber-Laser-Based Applications of Transition Metal Dichalcogenide Monolayers./
作者:	Kilinc, Muhammed Hasan.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	108 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-01, Section: B.
Contained By:	Dissertations Abstracts International83-01B.
標題:	Materials science. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28499148
ISBN:	9798516935862

Nonlinear Optical Properties and Fiber-Laser-Based Applications of Transition Metal Dichalcogenide Monolayers.
Kilinc, Muhammed Hasan.

Nonlinear Optical Properties and Fiber-Laser-Based Applications of Transition Metal Dichalcogenide Monolayers. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 108 p.

Source: Dissertations Abstracts International, Volume: 83-01, Section: B.

Thesis (Ph.D.)--State University of New York at Buffalo, 2021.

This item must not be sold to any third party vendors.

In this dissertation, nonlinear optical properties of two-dimensional Transition Metal Dichalcogenide (TMD) monolayers is investigated. We described the features and mechanisms observed in TMD monolayers leading to a direct bandgap, a large exciton binding energy and a nonzero second-order nonlinear response. The orbital arrangement and the crystal properties are explained in order to lay the foundation for the observed phenomena. A simple electron-atom anharmonic oscillator model is included to describe the origin of second harmonic generation (SHG) in TMD monolayers. Experimental methods such as PL mapping, polarization-resolved SHG mapping are described in detail. The experimental section includes a subsection where hyperspectral imaging of a TMD flake on a fiber tip is described. This setup allows one to reliably locate monolayer flakes and gives an insight into the flake thickness in few-layered flakes. In addition, we described how the photoluminescence response of a TMD flake placed on a fiber is transmitted and collected through a single-mode polarization-maintaining fiber. This demonstration shows the promising integration of TMD monolayers onto optical waveguides such as fibers. We have verified the previously reported optical properties such as high photoluminescence response at room temperature, indirect to direct bandgap transition, high second-order nonlinear susceptibility. We introduced the alloyed TMD monolayers where the composition of the triangular CVD grown flakes varies in the radial direction. We utilized the ratio of two prominent peaks in the Raman spectra as a metric to quantify the material variation. In contrast to both Raman peak ratio and photoluminescence peak maps, SHG intensity maps turned out to be uniform for a given fundamental beam polarization. In addition to those, we found that polarization resolved SHG mapping can be used as a sensitive tool to probe the mechanical strain in TMDs. As TMD monolayers have been shown to have localized single photon emission due to applied mechanical strain, mapping the mechanical strain over a TMD monolayer is an important step in finding possible single photon emission locations on a given sample. We also reported preliminary results regarding exciton lifetimes in alloyed TMD monolayers. The monolayer alloy is shown to have a fast lifetime of about 30–50 ps which is one order of magnitude shorter than reports in the literature. As the lifetime of the exciton is affected by a combination of factors such as the dielectric nature of the substrate, defects, non-radiative recombination channels, temperature and material composition, it turned out to be a challenging task to accurately measure the lifetime with a streak camera where the lifetime precision is limited by 20 ps. We also demonstrated intracavity second harmonic generation by placing a TMD monolayer in a fiber laser cavity. The monolayer was fabricated using the Scotch tape method and verified as a monolayer using photoluminescence spectroscopy. We showed that very little SHG light is present without the monolayer in the cavity, while in the presence of the monolayer, the SHG light increases quadratically with peak power as predicted by theory. We therefore demonstrated an intracavity SHG process that is inherently phase matched inside of a mode locked fiber laser and showed that the monolayer greatly enhanced SHG performance with minimal negative effects on the fiber laser. This novel structure takes advantage of the greatly enhanced intracavity intensities inside of the fiber laser cavity to increase SHG efficiency. As fiber-laser frequency-combs have been an emerging technology in recent years, we can argue that TMD monolayers can be used as second harmonic generators in the cavity of fiber lasers for the detection of carrier envelope offset, therefore realize a compact and robust frequency standard. The two main findings of this study, the use of SHG mapping to probe strain and combining TMD monolayers with optical fibers, are laying the foundation of a new platform for fiber-integrated single photon emitters. As a step forward following our results, one can study the effect of strain on TMD monolayers and pinpoint the stress points which are likely to be emitting single photons. Furthermore, it would be possible to pattern the tip of an optical fiber in a way so that it induces strain on a TMD flake placed on the fiber tip. Such a study would be an interesting development which is promising for quantum optics and communication applications.

ISBN: 9798516935862Subjects--Topical Terms:

557839
Materials science.
Subjects--Index Terms:

2D materials

Nonlinear Optical Properties and Fiber-Laser-Based Applications of Transition Metal Dichalcogenide Monolayers.
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520 $a In this dissertation, nonlinear optical properties of two-dimensional Transition Metal Dichalcogenide (TMD) monolayers is investigated. We described the features and mechanisms observed in TMD monolayers leading to a direct bandgap, a large exciton binding energy and a nonzero second-order nonlinear response. The orbital arrangement and the crystal properties are explained in order to lay the foundation for the observed phenomena. A simple electron-atom anharmonic oscillator model is included to describe the origin of second harmonic generation (SHG) in TMD monolayers. Experimental methods such as PL mapping, polarization-resolved SHG mapping are described in detail. The experimental section includes a subsection where hyperspectral imaging of a TMD flake on a fiber tip is described. This setup allows one to reliably locate monolayer flakes and gives an insight into the flake thickness in few-layered flakes. In addition, we described how the photoluminescence response of a TMD flake placed on a fiber is transmitted and collected through a single-mode polarization-maintaining fiber. This demonstration shows the promising integration of TMD monolayers onto optical waveguides such as fibers. We have verified the previously reported optical properties such as high photoluminescence response at room temperature, indirect to direct bandgap transition, high second-order nonlinear susceptibility. We introduced the alloyed TMD monolayers where the composition of the triangular CVD grown flakes varies in the radial direction. We utilized the ratio of two prominent peaks in the Raman spectra as a metric to quantify the material variation. In contrast to both Raman peak ratio and photoluminescence peak maps, SHG intensity maps turned out to be uniform for a given fundamental beam polarization. In addition to those, we found that polarization resolved SHG mapping can be used as a sensitive tool to probe the mechanical strain in TMDs. As TMD monolayers have been shown to have localized single photon emission due to applied mechanical strain, mapping the mechanical strain over a TMD monolayer is an important step in finding possible single photon emission locations on a given sample. We also reported preliminary results regarding exciton lifetimes in alloyed TMD monolayers. The monolayer alloy is shown to have a fast lifetime of about 30–50 ps which is one order of magnitude shorter than reports in the literature. As the lifetime of the exciton is affected by a combination of factors such as the dielectric nature of the substrate, defects, non-radiative recombination channels, temperature and material composition, it turned out to be a challenging task to accurately measure the lifetime with a streak camera where the lifetime precision is limited by 20 ps. We also demonstrated intracavity second harmonic generation by placing a TMD monolayer in a fiber laser cavity. The monolayer was fabricated using the Scotch tape method and verified as a monolayer using photoluminescence spectroscopy. We showed that very little SHG light is present without the monolayer in the cavity, while in the presence of the monolayer, the SHG light increases quadratically with peak power as predicted by theory. We therefore demonstrated an intracavity SHG process that is inherently phase matched inside of a mode locked fiber laser and showed that the monolayer greatly enhanced SHG performance with minimal negative effects on the fiber laser. This novel structure takes advantage of the greatly enhanced intracavity intensities inside of the fiber laser cavity to increase SHG efficiency. As fiber-laser frequency-combs have been an emerging technology in recent years, we can argue that TMD monolayers can be used as second harmonic generators in the cavity of fiber lasers for the detection of carrier envelope offset, therefore realize a compact and robust frequency standard. The two main findings of this study, the use of SHG mapping to probe strain and combining TMD monolayers with optical fibers, are laying the foundation of a new platform for fiber-integrated single photon emitters. As a step forward following our results, one can study the effect of strain on TMD monolayers and pinpoint the stress points which are likely to be emitting single photons. Furthermore, it would be possible to pattern the tip of an optical fiber in a way so that it induces strain on a TMD flake placed on the fiber tip. Such a study would be an interesting development which is promising for quantum optics and communication applications.
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