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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 9: Focus: Polar oxide crystals and solid solutions
KFM 9.8: Vortrag
Mittwoch, 18. März 2020, 12:00–12:20, TOE 317
Superposed picosecond luminescence kinetics in lithium niobate — •Andreas Krampf, Simon Messerschmidt, and Mirco Imlau — University of Osnabrueck, Department of Physics, Barbarastrasse 7, 49076 Osnabrueck, Germany
Various manifestations of small polarons strongly affect the linear and nonlinear optical properties in the oxide crystal lithium niobate (LiNbO3, LN). Whereas related transient-absorption phenomena in LN have been studied extensively in the last decades, a sound microscopic picture describing the blue-green (photo)luminescence of lithium niobate single crystals is still missing. In particular, nearly nothing is known about: (i) the luminescence build-up and (ii) its room temperature decay. We here present the results of our systematic experimental study using nominally undoped and Mg-doped LN crystals with different Mg concentration. Picosecond luminescence was detected by means of femtosecond fluorescence upconversion spectroscopy (FLUPS) extended to the inspection of oxide crystals in reflection geometry.
Taking the recently proposed microscopic model into account, which describes luminescence decay in LN by local radiative self-trapped exciton recombination and/or migration and subsequent pinning on defect sites, a detailed analysis of the kinetic traces reveals, that the picosecond luminescence decay represents the superposition of exponential and stretched-exponential decay paths.
We critically discuss the data considering the interplay with small polaron transport. Financial support by the DFG (IM37/11-1, INST 190/165-1 FUGG) is gratefully acknowledged.