Berlin 2012 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 13: Poster II

DF 13.19: Poster

Mittwoch, 28. März 2012, 15:00–17:30, Poster E

Transient absorption and nonlinear refractive index changes in nominally pure, thermally reduced LiNbO₃ induced by sub-100-fs light pulses — •Holger Badorreck, Volker Dieckmann, Pia Baeune, and Mirco Imlau — Department of Physics, University of Osnabrück, Germany

Nominally undoped lithium niobate—as grown and thermally reduced—is of great interest for ultrafast optical devices due to its polaronic features. With formation times in the sub-ps-range short-lived small polarons can be generated in reduced samples by optical gating of bipolarons due to single photon absorption. Simultaneously, formation of small hole polarons by two-photon-absorption is observed. In this work nonlinear absorption and refractive index changes due to exposure to sub-100-fs light pulses of 488 nm are presented in presence of a considerable number density of bipolarons. It is found that the two-photon absorption coefficient is not affected by the thermal reduction procedure, whereas the nonlinear refractive index change is considerably smaller in the reduced sample compared to the unreduced one. We further present our results on the study of the transient absorption in the blue and NIR spectral range by means of fs-pump-probe technique. The influence of the thermal reduction procedure on lifetime and densities of electron and hole polarons is discussed.

Financial support by the DFG (IM 37/5, INST 190/137-1) is gratefully acknowledged.