A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree Master of Science, 2017 / Three thulium-doped fibre lasers (TDFLs) were developed: a large mode area (LMA) 25/400 “test” TDFL, a high power cw TDFL, and a Q-switched TDFL. For the test TDFL, the relationship between self-pulsing in TDFLs and laser reabsorption effects were explored by way of spectral and temporal measurements. Laser design aspects and technical procedures were also investigated. The highly efficient, high power cw TDFL produced a pump limited output power of 63 W with a slope efficiency of ~56 %. Thermal management schemes including splicing and fibre cooling were discussed and implemented. A polarisation maintaining thulium-doped fibre (TDF) was implemented for the Q-switched TDFL which produced pulse lengths of ~207 ns and peak powers of 1.17 kW at ~23 W of average laser output power. Gain switching of the Q-switched TDFL pump diodes further reduced the output pulse length to ~163 ns with peak powers of 1.35 kW. / XL2017

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Thesis (Ph. D. in Chemistry)--University of California, Berkeley, June 1961. / "UCRL-9203." Includes bibliographical references (leaves 151-153).

Th.--Sci. phy.--Grenoble 1, 1980. N°: 57.

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Th.--Sci phys.--Grenoble 1, 1980. N°: 56. / Extr. en partie de Journal de physique. Colloque C5, 40, 1979, 5, 364-365 ; 41, 1980, 6, 181-184 ; de Physical review letters, 43, 1979, 4,304-307 ; de Journal of magnetism and magnetic materials, 1980, 989-990 et de Valence instabilities and narrox band phenomena, 1977, 513-515.

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A Thulium Germanate thin disk laser prototype is developed and its potential applications are discussed. Unfortunately, the thin disk gain material for the CW prototype was unable to lase due to thermal limitations within the disk. However, a CW output power model and a physical pump chamber module have been developed, along with the supporting Zemax models and alignment procedures so other gain materials and future improvements can be tested.

The purpose of this investigation was to study the radiations of the 169/Tm nucleus as it de-excites after the electron capture decay of the 169/Yb. Numerous unreported gammas were present in the sample. The origins of these gamma rays were found.