Determining rare earth dopant concentrations in optical fibres and waveguides

The fluorescence lifetimes of rare earth-doped fibres and waveguides were studied in this thesis to determine whether the fluorescence lifetime could be used as a means for determining the rare earth concentrations. The performance of rare earth-doped devices is dependent on many parameters, including the dopant concentration. Accurate modelling of such devices require knowledge of the dopant concentrations and/or dopant distribution. Current techniques for determining dopant concentration are applicable to bulk samples and fibre preforms but can not be applied to fibres due to fibre size and resolution limits. A technique was proposed by researchers within this research group that used the fluorescence lifetimes of praseodymium-doped fibres. Their work found that the lifetime of the lifetime of praseodymium-doped ZBLAN fibre increased linearly with praseodymium concentration. These results showed promise in the use of fluourescence lifetimes as a method for determining both the absolute concentration as well as imaging the concentration profile using confocal microscopy. This technique is explored further in this work to see if it could be applied to other rare earths