Regensburg 2010 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 15: Optical and nonlinear optical properties, photonics II
DF 15.6: Vortrag
Donnerstag, 25. März 2010, 12:10–12:30, H11
Transient light–induced absorption in thermally reduced, periodically poled lithium niobate doped with yttrium — •Bettina Schoke1, Mirco Imlau1, Christoph Merschjann2, Garbor Corradi3, Katalin Polgar3, and Inna Naumova4 — 1Physics Department, University of Osnabrück, Germany — 2Helmholtz-Zentrum Berlin GmbH, Germany — 3Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences Budapest, Hungary — 4Physics Department, Moscow State University, Russia
Excitation and recombination processes of small polarons are studied in thermally reduced, periodically poled LiNbO3 doped with Y (PPLN:Y). The reduction treatment creates bipolarons (NbLi4+:NbNb4+) which are stable at room temperature. They may be dissociated optically into small bound (NbLi4+) and free (NbNb4+) polarons (”optical gating”). The light-induced absorption arising from the population and depopulation of these centers is measured time–resolved via transient absorption spectroscopy in the blue and red spectral range after optical excitation with intense laser pulses (λ = 532 nm, t = 8 ns). Besides dissociation and relaxation of bipolarons the investigations also indicate the presence of photo-induced hole polarons (O−) with comparatively longer lifetime. The findings can be explained by a periodic spatial modulation of the NbLi5+ antisite concentration and of the degree of reduction. Both modulations most likely result from a periodic incorporation of Y ions on Li sites. *Financial support by the DFG (IM 37/5-1, GRK695) is gratefully acknowledged.