Pulse generation in 1.55 μm region using a metal carbide absorber / Muhammad Afiq Ashraf Badsha Sahib

Muhammad Afiq Ashraf, Badsha Sahib (2023) Pulse generation in 1.55 μm region using a metal carbide absorber / Muhammad Afiq Ashraf Badsha Sahib. Masters thesis, Universiti Malaya.

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Abstract

Attributed to their unique properties of compact structure, good flexibility, and low cost, pulsed fiber lasers are excellent light sources for various applications, such as optical communications, biology or medical sciences, micromachining etc. Passive Q-switching and mode-locking techniques are two common methods for generating pulsed lasers, with the key component of a saturable absorber (SA). Titanium silicon carbide (Ti3SiC2) MAX phase and titanium carbide (Ti3C2Tx) MXene are typical transition-metal carbide materials with excellent nonlinear and temperature resilience characteristics, which are emerging as promising saturable absorption materials for pulsed fiber lasers. In this dissertation, Ti3SiC2 and Ti3C2Tx have been used to develop thin film based SAs using a drop casting technique while using a PVA as a host polymer. The fabricated Ti3SiC2 and Ti3C2Tx thin films have a modulation depth of 51 %, 4.8 %, respectively and thus suitable for Q-switching and mode-locking applications. By integrating the prepared Ti3SiC2/PVA thin film into an EDFL cavity, stable Q-switched pulses operating at 1561.8 nm were obtained and the maximum energy of 100.7 nJ was achieved at a repetition rate of 43.5 kHz. The minimum pulse width of the output pulses was 5.6 μs at a pump power of 71.5 mW. The Ti3SiC2 PVA thin film also capable of achieving picosecond pulse when integrated with the extended EDFL ring cavity with a length of 106 m. The proposed mode locked EDFL operated at repetition frequency of 1.88 MHz with a pulse width of 3.03 ps, maximum pulse energy of 6.0 nJ and maximum peak power of 2.0 kW. This study also successfully demonstrated the use of a Ti3C2Tx MXene SA for Q-switching application. The results show that the SA successfully produces Q-switched laser pulses with a pulse width of 3.11 μs and repetition rate of 65.59 kHz at the input pump power of 66.3 mW. At the same pump power, the pulse energy is 125 nJ and the maximum output power is 8.17 mW. It is also found that the Ti3C2Tx PVA SA successfully produces mode-locked pulses within a pump power from 40.2 mW to 87.2 mW. It operates at 1561.2 nm with a repetition rate of 1.89 MHz and pulse width of 154 ns. At 87.2 mW pump power, the average output power, pulse energy and peak power is 11.85 mW, 6.24 nJ, and 40.7 mW, respectively. These results validated the simplicity and feasibility of both SAs for producing a stable Q-switched and mode-locked pulse train.

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