Construction and Passive Q-Switching of a Ring-Cavity Erbium-Doped Fiber Laser Using Carbon Nanotubes as a Saturable Absorber

The purpose of this thesis is to design, build, test, and achieve pulsed operation of a ring-cavity erbium-doped fiber laser using carbon nanotubes as a saturable absorber. The erbium-doped fiber is characterized first, cross-sections are calculated, and the gain value is determined. Subsequently, the ring cavity is constructed and the laser is operated in the continuous wave regime. Much time is then spent trying to characterize and utilize the carbon nanotubes successfully. Many dispersions are made using multiple solvents and dispersing media, various images are taken with both scanning electron and Raman microscopy, and attempts at purification are made. Saturable absorbers are then created both by coating the end facet of a fiber with a dispersion containing carbon nanotubes and by inserting a fabricated poly-methyl-methacrylate (PMMA) and singlewalled carbon nanotube (SWCNT) polymer composite film between two fiber end facets. Once inserted into the cavity, the saturable absorbers passively Q-switch the laser in three distinct cases. A fiber end facet coating of SWCNTs dispersed into isopropanol produced pulses with duration of 17.45 ± 0.11 μs and 2.74 ± 0.14 μs, with repetition rates of 25.36 ± 0.53 kHz and 37.77 ± 0.33 kHz, respectively. A second fiber end facet coating of SWCNTs dispersed into dimethylformamide (DMF) produced pulses with duration of 12.28 ± 1.08 μs and 3.58 ± 0.12 μs, with repetition rates of 25.13 ± 0.63 kHz and 26.46 ± 0.13 kHz, respectively. The PMMA plus SWCNT polymer composite film produced pulses of 0.716 ± 0.007 μs duration and 142.8 ± 1 kHz repetition rate