| Author: | Wang, Xinyu |
| Title: | Optical performances of group-10 transition metal dichalcogenides materials |
| Advisors: | Tsang, Y. H. (AP) |
| Degree: | Ph.D. |
| Year: | 2020 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Transition metal compounds |
| Department: | Department of Applied Physics |
| Pages: | xvi, 128 pages : color illustrations |
| Language: | English |
| Abstract: | Two-dimensional (2D) layered transitional metal dichalcogenides (TMDs) materials have shown considerable potential in various optical performances. Among them, platinum disulfide (PtS2), which is newly developed group-10 2D layered TMDs materials, offers great potential for the laser photonic applications owing to its high carrier mobility, broadly tunable natural bandgap energy, and stability. Numerous studies have been conducted to explore the performance of 2D layered nano-materials based saturable absorber (SA) for pulsed laser applications, recently. The study of pulsed laser performance based on the SA prepared by layered materials with bulk-micro sizes have gained a great attention due to the simple preparation process, low energy consumption and simple expertise. Hence, in the first part of this study, the first passively Q-switched Erbium doped fiber laser is demonstrated with an operational wavelength of 1568.8 nm by using PtS2 microflakes SA, fabricated by a simple liquid exfoliation in N-Methyl-2-pyrrolidone (NMP) and then incorporated into polyvinyl alcohol polymer thin film. A stable Q-switched laser operation is achieved by using this PtS2-SA within a fiber laser ring cavity. The maximum average output power is obtained as 1.1 mW, corresponding to the repetition rate of 24.6 kHz, pulse duration of 4.2 µs, and single pulse energy of 45.6 nJ. The achievement in Q-switched application arouses my interest in further exploration on other optical potential of PtS₂. It is reported that photoluminescence (PL) behaviour of PtS2 still remains obscure. Inspired by other works on TMDs quantum dots (QDs), which are believed having the capability to enhance PL property compared to the bulky or layered structure owing to their quantum confinement effects, the fabrication of PtS₂ QDs suspension via a low-cost liquid exfoliation technique is demonstrated in this work. The PtS₂ QDs with an average diameter of 3.9 nm and average thickness of 2.9 nm are observed, respectively. For the first time, the PL spectra of PtS₂ QDs suspension are successfully obtained and monitored over time. The PL spectra display an excitation-dependent luminescence. The maximum emission peak is observed at 407.2 nm for the excitation wavelength of 330 nm. This PtS₂ QDs also shows a decent long-term stability. The next part of this study moves to expand the PL research from PtS₂ to other group-10 TMDs materials, so far whose PL natures of QDs structure still remain to be revealed. In this study, 3 typical types of group-10 TMDs materials (PtS₂, PdS₂, and PdSe₂) QDs are fabricated via liquid exfoliation using NMP solvent. The absorption and PL spectra of these QDs solutions are studied, exhibiting excitation wavelength-dependent behavior and large stokes shifts. Furthermore, the quantum yield and decay lifetime are also investigated and analyzed. The obtained results suggest promising optical performances of group-10 TMDs materials and indicate their prospective applications in the future. |
| Rights: | All rights reserved |
| Access: | open access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 991022378658303411.pdf | For All Users | 4.15 MB | Adobe PDF | View/Open |
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