Laser Phenomena in Europium Chelates. II. Kinetics and Optical Pumping in Europium Benzoylacetonate

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Abstract
The laser application of europium chelates is considered in some detail by means of an analysis of the steady‐state kinetics of the fluorescence and of the optical pumping. An energy‐level model of the chelate molecule is proposed and the kinetics analyzed in terms of the various transition probabilities. The solutions for the steady state indicate the effect of the various transition probabilities on the threshold for laser action. It is also pointed out that the triplet state associated with the phosphorescence can function as a trap state. A consideration of the pumping problem reveals that the intense absorption leads to extremely non‐uniform excitation which reduces the width of the effective pump band. The rate of pumping becomes relatively insensitive to concentration but is extremely dependent on the diameter of the cylindrical optical cavity. These considerations are then applied to a comparison of the thresholds for laser action in ruby and EuB.