Regensburg 2016 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 3: Optical and nonlinear optical properties, photonic
DF 3.2: Talk
Monday, March 7, 2016, 09:50–10:10, H26
Luminescence of undoped lithium niobate — •Simon Messerschmidt, Andreas Krampf, and Mirco Imlau — Department of Physics, Osnabrück University, Germany
Luminescence of lithium niobate (LN) was studied for the first time 1973 by Blasse [Blasse, G. Phys. Stat. Sol. (a) 20, K99 – K102 (1973)]. He detected a broadband light emission of LN under UV-excitation at temperatures below 80 K and assumed that the origin of the luminescence lies in the NbO6-octahedron. Various authors subsequently have found a connection between the ratio of [Li]/[Nb] and the emitted peak wavelengths so that the red-shift in lithium-poor LN is interpreted as a disturbance of the NbO6-octahedron (NbLi-antisite defect). The emitted light is independent of the excitation wavelength and has a large Stokes shift. Therefore, the luminescence is described in a model of a self-trapped exciton (STE) [Wiegel, M., et al., J. Phys. Chem. Solids 55, 773 – 778 (1994)]. Until now, the interplay of STE and small polarons as well as parameters such as duration of the excitation pulse or crystal morphology to control the probability of the luminescence is unknown which is the topic of this work. Two experimental setups are used and initial results are presented. In the first setup, ns-pulses were used to excite a sample cooled to T=30 K whose emitted light is detected with a gated photon counter. In a second setup, a luminescence upconversion detector utilizing ultrashort femtosecond pulses is applied to detect the dynamics of the luminescence light. Financial support by the DFG (IM 37/5-2, INST 190/165-1 FUGG) is gratefully acknowledged.