Energy-transfer upconversion and thermal lensing in high-power end-pumped Nd:YLF laser crystals

P.J. Hardman, W.A. Clarkson, G.J. Friel, Markus Pollnau, D.C. Hanna

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    Thermal lensing in an end-pumped Nd:YLF rod, under lasing and nonlasing conditions, has been investigated. Under lasing conditions, a weak thermal lens, with dioptric power varying linearly with pump power, was observed. Under nonlasing conditions, where higher inversion densities were involved, hence relevant to Q-switched operation or operation as an amplifier, a much stronger thermal lens was measured, whose power increased nonlinearly with pump power. This difference has been attributed to the increased heat deposition due to the subsequent multiphonon decay following various interionic upconversion processes, which increase strongly under nonlasing conditions, and is further exacerbated by the unfavorable temperature dependencies of heat conductivity and the rate of change of the refractive index with temperature. A strategy for reducing upconversion and its associated thermal loading, without degrading laser performance, is discussed.
    Original languageUndefined
    Pages (from-to)647-655
    Number of pages9
    JournalIEEE journal of quantum electronics
    Issue number4
    Publication statusPublished - 1999


    • IOMS-APD: Active Photonic Devices
    • Lasers
    • neodymium:solid-state lasers
    • laser amplifiers
    • IR-70101
    • EWI-17567
    • Diode pumped lasers
    • Upconversion
    • laser thermal factors

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