Rare-Earth Oxide Ion (Tm3+, Ho3+, and U3+) Doped Glasses and Fibres for 1.8 to 4 Micrometer Coherent and Broadband Sources

This report results from a contract tasking University of Leeds as follows Task 1 0-5 months Optimise tellurium oxide TeO2, fluorine-containing silicate SiOF2 and germanate GeOF2 glass hosts for each dopant by characterising the spectroscopic properties, including absorption and emission cross-sections and the lifetimes of the lasing levels. Design multimode fibres for the analysis of pump photon ion interaction, and for examining any detrimental effects. A preliminary investigation on various pumping schemes using semiconductor diode laser wavelengths at 800 nm, 940 nm, 960 nm, 980 nm, 1480 and 1550 nm will be explored. Deliverable Report 1 A comparison of the spectroscopic properties of RE-ion doped Tm3, Ho3, and U3 and their suitability for tunable laser source. Task 2 6th-7th month Multimode fibres will be drawn to study the interaction of pump photons in a long interaction path length, from which we will be able to investigate the potential sources of ESA, favourable or detrimental energy transfer and pumping scheme. Also consider whether all the dopants should be incorporated in a single core, or to have each dopant in a separate core around a common cladding, so that the high-power pump source can provide sufficient excitation for Tm3, Ho3, and U3 acceptor ions and Yb3 as the sensitizer ions. Task 3 8th-9th month Quantify the quantum efficiency of individual transitions in the dopants. Using carefully designed fibres with Ho or Tm, undertake a preliminary investigation of the laser experiment and establish the required threshold and slope efficiency in either Tm-doped or Ho-doped fibres. Deliverable report 2 Summary of fibre spectroscopy and preliminary gain characterisation using a suitable pumping scheme.