Generation of tunable q-switched erbium-doped fiber laser based on graphite flakes saturable absorber

• Main Author: Nik Mahmud, Nik Noor Haryatul Eleena
• Format: Thesis
• Language: English; English; English
• Published: 2020
• Subjects: QC350-467 Optics. Light
• Online Access: http://eprints.uthm.edu.my/405/1/24p%20NIK%20NOOR%20HARYATUL%20ELEENA%20NIK%20MAHMUD.pdf; http://eprints.uthm.edu.my/405/2/NIK%20NOOR%20HARYATUL%20ELEENA%20NIK%20MAHMUD%20WATERMARK.pdf; http://eprints.uthm.edu.my/405/3/NIK%20NOOR%20HARYATUL%20ELEENA%20NIK%20MAHMUD%20COPYRIGHT%20DECLARATION.pdf; http://eprints.uthm.edu.my/405/
• Institution: Universiti Tun Hussein Onn Malaysia

Pulsed fiber laser has tremendous application in laser processing and laser sensor. The key element to produce a passively Q-switched fiber laser is by using a saturable absorber (SA). Passively Q-switched fiber laser is the most desirable pulse in laser technology due to its ability to generate optical pulses in microsecond and nanosecond. The aim of this study is to construct a single ring erbium-doped fiber (EDF) laser based on graphite flakes SA to produce short pulse laser. Graphite flakes SA were prepared by mechanical exfoliation techniques and was transferred onto a fiber ferrule tip. The saturable absorption property of the graphite was measured using twin detector method which resulted in a modulation depth of 23.82% with a saturation intensity of 0.031 MW/cm2. Surface morphology, elemental analysis and absorbance characteristics of the graphite flakes were analyzed by the field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX) and ultraviolet visible spectroscopy (UV-VIS). The result showed that the carbon element on the SA has a very strong peak intensity. The two different EDF coefficient of 6.43 dB/m and 18.93 dB/m (EDF M-5 and EDF I-12) showed a repetition rate of 41.62 kHz and 60.00 kHz with a pulse width of 6.45 μs and 3.38 μs, respectively at a pump power of 268.8 mW. The wavelength tunability of passively Q-switched fiber laser for EDF M-5 and EDF I-12 were optimized at fixed pump power where the tuning range of EDF M-5 occurred between 1544 nm to 1560 nm and 1552 nm to 1570 nm for EDF I-12. The passively Q-switched fiber laser with different EDF coefficients were successfully constructed in a single ring configuration with more selection of wavelength that is up to L band by using higher EDF coefficient.