Münster 1997 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 2: Poster
DF 2.8: Poster
Dienstag, 18. März 1997, 10:15–13:00, Aula
Light-induced absorption in SBN:Cr crystals — •M. Gao, S. Kapphan, and R. Pankrath — FB Physik, Universit"at Osnabr"uck, 49069 Osnabr"uck
SBN crystals with open tungsten-bronze structure show enhanced photorefractive properties with doping impurities like Ce, Cr, Rh etc. Cr-doped SBN is reported to have much faster response speed and higher two-beam coupling gain under external electric field compared with other SBN crystals [1]. The strong dichroic absorption of the Cr doping (λmax=654 nm) promises an enhanced red sensitivity for the photorefractive process in this material. However, the light-induced charge transport process in SBN:Cr is little investigated so far. Congruent SBN (x=0.61) with dopings of Cr from 50ppm to 0.1 wt.% in the melt, grown by our crystal growth laboratory, are investigated. Under the illumination of Kr+-laser light (647 nm) and Ar+-laser light (514 nm and 488 nm), SBN:Cr demonstrates a strong light-induced polaron absorption band around 6000 cm−1 at low temperatures. The polarization, intensity, temperature dependence and the kinetics of the build-up and decay process are studied in detail. A simplified working model explaining light-induced absorption in VIS and NIR regions in SBN:Cr is proposed.
This work is supported by DFG (SFB225, C7).
[1] K.Sayano, A.Yariv und R.R.Neurgaonkar, Appl. Phy. Lett. 55, 328 (1989)