Regensburg 2010 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 13: Poster II: Electrical, mechanical and optical properties, nonlinear dielectrics

DF 13.5: Poster

Mittwoch, 24. März 2010, 15:00–17:30, Poster A

Time-resolved analysis of short-living mixed phase and amplitude gratings — •Raphael-Sung Hardt, Hauke Bruening, Bettina Schoke, and Mirco Imlau — Department of Physics, University of Osnabrück, Barbarastr. 7, D-49069 Osnabrück, Germany

The time-resolved analysis of short-living mixed phase and amplitude gratings is a demanding challenge in materials with an optical response originating from optically excited, metastable states. For instance, such gratings appear in materials featuring the optical generation of strongly localized charge carriers or photo-induced linkage isomerism in molecular crystals. An established tool for volume grating analysis is the determination of the diffraction efficiency as a function of the angular detuning Δ θ_B from the Bragg angle θ_B, i.e., the so-called rocking curve. Fitting of the data set with appropriate functions allows to separate the individual contributions of phase and amplitude gratings to the overall diffraction efficiency and further yields information on a mutual phase shift. With thermally reduced, nominally undoped LiNbO₃ as an example we show our results on the time-resolved determination of the rocking curve in the time regime of 10⁻⁸ s to 10² s with a temporal resolution of up to 10 ns. The gratings are recorded by pulsed laser light (λ = 532 nm, τ = 8 ns ) and are probed in the near-infrared spectral range at λ = 785 nm. Grating analysis yields the temporal development of phase and amplitude gratings, which originate from optically generated small polarons.

*Financial support by the DFG (Projects IM37/5-1 and GRK 695) is gratefully acknowledged.