Quantifying Doping Non-Uniformity by Analyzing Spatially Dependent Energy Transfer Rates

Through the comparison of a suite of energy transfer rate parameters obtained from a series of solution-doped Tm 3+ -aluminosilicate glass fibers with a Tm 3+ -aluminosilicate fiber made using nanoparticle doping, we show quantitative evidence of doping non-uniformity. In relation to Tm 3+ , we find that energy transfer upconversion is more sensitive to spatial non-uniformities in the rare earth ion doping distribution compared to cross relaxation, which may be explained by high localization of excited Tm 3+ ions, leading to enhancement of the relative strength of the relatively weaker upconversion processes compared to the strong primary cross-relaxation process. Measurements of the fluorescence decay of the 3 F 4 , 3 H 4 , and 1 G 4 levels were completed, in addition to measurement of the 470 nm fluorescence rise time under 790 nm pumping. An analysis of these results using our method of extracting the energy transfer rate parameters enabled quantification of the rates of the energy transfer and energy migration processes relevant to the operation of 790 nm pumped Tm 3+ -doped fiber lasers emitting in the two-micron band.