Regensburg 2016 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 3: Optical and nonlinear optical properties, photonic

DF 3.3: Vortrag

Montag, 7. März 2016, 10:10–10:30, H26

Ultrafast holographic spectroscopy for the study of small polarons in lithium niobate — •Stefan Nolte, Bjoern Bourdon, Felix Freytag, and Mirco Imlau — School of Physics, Osnabrück University, Germany

The optical generation of small bound polarons in lithium niobate can be used to record holographic gratings with a single nanosecond laser pulse and a diffraction efficiency above 20 % [M. Imlau et al. Opt. Express 19, 15322 (2011), H. Brüning et al. Opt. Express 20, 13326 (2012)]. This finding is explained via the linear electro-optic effect and the space-charge field generated from a small polaron number density modulation with E ≈ 17 kV/cm. For the long-range transport of small polarons, we assume cascaded optical excitation during light exposure, i.e. the pulse duration has a strong impact on the hologram recording process [cf. H. Badorreck et al. Opt. Mater. Express 5, 2729 (2015)].

In this contribution, we study the holographic buildup as a function of pulse duration in the femtosecond time regime. Thus, a four-wave pump-probe experiment with continously varied pulse-durations between τ = (70−500) fs is used to record the time-dependent diffraction efficiency from a mixed holographic grating, based on nearly instantaneous nonlinearities χ⁽³⁾ and polaron effects. The results are disscussed under consideration of polaron formation.

Financial support by the DFG (IM 37/5-2, INST 190/165-1 FUGG) is gratefully acknowledged.