Generation of q-switched and soliton mode locked pulses with 8-hydroxyquinolino cadmium chloride hydrate and chromium aluminum carbide saturable absorber / Mustafa Mohammed Najm

Mustafa , Mohammed Najm (2022) Generation of q-switched and soliton mode locked pulses with 8-hydroxyquinolino cadmium chloride hydrate and chromium aluminum carbide saturable absorber / Mustafa Mohammed Najm. PhD thesis, Universiti Malaya.

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Abstract

This thesis describes the fabrication of new saturable absorber (SA) devices based on 8-Hydroxyquinolino cadmium chloride hydrate (8-HQCdCl2H2O) and chromium aluminum carbide (Cr2AlC) materials and test them in a ring-cavity Erbium-doped fiber laser (EDFL) for Q-switching and mode-locking applications. This study aims to develop an efficient and low-cost Q-switched and mode-locked fiber lasers operating in the nanosecond and picosecond regime, respectively using the newly developed SAs. The SAs are fabricated first using mechanical exfoliation and thin film methods, their physical, chemical, and optical characteristics are then investigated. The modulation depth of the exfoliated 8-HQCdCl2H2O on scotch tape, 8-HQCdCl2H2O thin film and Cr2AlC thin film are obtained at 11 %, 18 % and 3.2 %, respectively, indicating their suitability for Q-switching and mode-locking applications. Subsequently, the ring cavity is constructed using an Erbium-doped fiber as the gain medium, and the prepared SA is integrated and optimized into the laser cavity for Q-switched nanosecond and soliton pulse generations. Much time is then spent trying to optimize the cavity and utilize the 8-HQCdCl2H2O and Cr2AlC SAs successfully. The nanosecond pulse generation was successfully realized using the 8-HQCdCl2H2O or Cr2AlC film as SA. The Q-switched laser produced 726 ns pulses with a repetition rate of 150 kHz at pump power of 167 mW with 8-HQCdCl2H2O thin film. By optimizing EDFL cavity, mode-locked pulse train operating in 1.5 μm region with a pulse width within picosecond to femtosecond regime was successfully realized using the newly developed 8-HQCdCl2H2O and Cr2AlC SAs. These SAs successfully used to demonstrate different mode locked pulses in different EDFL cavities. For instance, femtosecond soliton pulses were obtained in the 33 m EDFL cavity. The laser produced a soliton pulse with the full width at half-maximum (FWHM) of 950 fs at a repetition rate of 5.6 MHz. These fiber lasers have many potential applications in various fields including biomedical imaging, material processing, and optical communication.

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