Direct upper-state pumping of the 2.8 mu m, Er/sup 3+/:YLF laser

Direct resonant pumping of the /sup 4/I/sub 11/2/ upper state of the 2.8- mu m Er/sup 3+/:YLF laser at 0.97 mu m is shown to be more efficient than other pumping schemes which have been used for this transition. Upper-state pumping avoids nonradiative losses arising from phonon and self-quenching decays inherent in other pumping schemes. Efficient performance of the 2.8- mu m laser is maintained on condition that extremely shallow pump absorption is avoided. Reduced efficiency for shallow pump absorption is attributed to upconversion loss arising from high pumping rates.<
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