Berlin 2012 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 13: Poster II
DF 13.18: Poster
Wednesday, March 28, 2012, 15:00–17:30, Poster E
Transient absorption in Sn2P2S6 induced by sub-100-fs light pulses — •Volker Dieckmann1, Holger Badorreck1, Mirco Imlau1, and Alexandr Shumelyuk2 — 1Department of Physics, University of Osnabrück, Germany — 2Institute of Physics, National Academy of Science, Kyiv, Ukraine
The interaction of sub-100-fs light pulses with single crystals of nominally undoped Sn2P2S6 is studied in the NIR spectral range (590−1630 nm) [1]. A predominant contribution of the two-photon absorption (TPA) is verified. The TPA coefficient β increases in a superlinear way for photon energies ℏω exceeding Eg/2; for any photon energy it is nearly independent of propagation direction and polarization of the incident beam. The TPA coefficient saturates at a maximum value of β≈8 cm GW−1 at ℏω≈ 1.8 eV. It drops when reaching the bandgap Eg. The TPA coefficients are higher by a factor of two than the values reported for other wide bandgap ferroelectrics, such as LiNbO3, while being lower in comparison to semiconductor crystals. Using pump-probe measurements at 626 nm, a transient absorption is observed that persists for probe pulse delays much longer than the pump pulse duration, up to 2.5 ns. Such transients are typical for a variety of wide bandgap ferroelectrics, where they are described by optically generated polaronic states. We discuss our results in the framework of the microscopic structure of Sn2P2S6 with emphasis on the optical generation of S− small hole polarons. Financial support by the DFG (IM 37/9-1, INST 190/137-1) is gratefully acknowledged.
[1] M. Imlau et al. Opt. Mater. Express 1, 953 (2011)