Date of Award
1-1-2017
Thesis Type
phd
Document Type
Thesis (Restricted Access)
Divisions
eng
Department
Faculty of Engineering
Institution
University of Malaya
Abstract
This research work focuses on exploring various new nanomaterials for saturable absorber (SA) application in generating Q-switched and Mode-locked pulses operating at 1 μm region. These nanomaterials are Molybdenum disulfide (MoS2), Black Phosphorus (BP), Topological Insulator (TI): Bismuth (III) Selenide (Bi2Se3), Bismuth (III) Telluride (Bi2Te3), and antimony telluride (Sb2Te3), and metal oxide: Nickle Oxide (NiO) nanoparticles and cobalt oxide (Co3O4) nanocubes. The fiber laser employs Ytterbiumdoped fiber (YDF) as a gain medium. Firstly, molybdenum disulfide (MoS2) was proposed. The Q-switched laser was obtained by using few layers MoS2, which was mechanically exfoliated by using a scotch tape. The SA was sandwiched between two fiber ferrules to form a fiber compatible Q-switcher. By incorporating the SA inside the YDFL cavity, a stable pulse laser operating at 1070.2 nm wavelength was generated with the repetition rate was tunable from 3.817 to 25.25 kHz. A passively mode-locked YDFL was demonstrated using a few layered MoS2 film which was obtained by a liquid phase exfoliation technique. The mode-locking pulses have a repetition rate of 18.8 MHz and pulse energy of 0.1 nJ. Secondly, mechanically exfoliated Black phosphorus (BP) was proposed for both Q-switching and mode-locking pulses generation. The Q-switched laser has a pump threshold of 55.1 mW, a pulse repetition rate that is tunable from 8.2 to 32.9 kHz, the narrowest pulse width of 10.8 μs and the highest pulse energy of 328 nJ. BP based mode-locked YDFL was obtained by improving the SA preparation. The laser operated at 1033.76 nm with a fixed repetition rate of 10 MHz. Passively Q-switched YDFLs was also successfully demonstrated using a few-layers Bi2Se3, Bi2Te3 and antimony telluride (Sb2Te3) based SAs. For instance, a Sb2Te3 film based Q-switched YDFL produced pulse repetition rate, which was tunable from 24.4 to 55 kHz with the maximum pulse energy of 252.6 nJ at 82.3 mW pump power. The mode-locked YDFL operating at 24.2 MHz repetition and 18.8 ps pulse width were also realized with Sb2Te3 based SA. Finally, two transition metal oxide nanomaterials: Nickel Oxide (NiO) and cobalt oxide (Co3O4) were embedded into a polymer film, making it an SA device for both Q-switched and mode-locked YDFLs. Stable Q-switched and mode-locked YDFLs were realized with both materials. For instance, the mode-locked Co3O4 based YDFL was operated at 1035.8 nm wavelength with a fixed repetition rate of 20 MHz and picoseconds pulse width. In short, an efficient and low-cost Q-switched and mode-locked YDFLs operating in 1 μm region have been successfully achieved by utilizing various new nanomaterials as SA.
Note
Thesis (PhD) – Faculty of Engineering, University of Malaya, 2017.
Recommended Citation
Ahmed Hasan, Hamood al-Masoodi, "Q-switching and mode-locking pulse generation in Ytterbium-doped fiber lasers using nanomaterial saturable absorbers / Ahmed Hasan Hamood al-Masoodi" (2017). Student Works (2010-2019). 4166.
https://knova.um.edu.my/student_works_2010s/4166