Regensburg 1998 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
DF: Dielektrische Festkörper
DF 6: Poster
DF 6.11: Poster
Donnerstag, 26. März 1998, 09:30–12:30, A
Chromium doping effects in SBN crystals — •J. Seglins1, S. Mendricks2, R. Pankrath2, V. Vikhnin3, and S. Kapphan2 — 1University of Riga, Kengaraga 8, 1234 Riga, Lettland — 2FB Physik, University of Osnabrück, Barbarastraße 7, D-49069 Osnabrück, Germany — 3Ioffe Institute, 194 021 St. Petersburg, Russia
Strontium-Barium-Niobate crystals posses some of the highest photorefractive and thermooptical nonlinearities; to employ them a increase of the light absoption is essential. Doping of Ce, Mn, Cu, Fe increases the light absorption only in the blue-green region of spectrum. Cr doping, besides the shift of the fundamental absorption edge of SBN to longer wavelengths, induces broad anisotropic absorption bands centered at 630 and 655 nm and reaching even 800 nm. This spectral region is corresponding to the most common semiconductor lasers. At the same time 2% Cr doping decreases the maximum temperature of the dielectric constant (at 1 kHz) to -15 ∘C from 84 ∘C in nominally pure SBN. Possible mechanism of at room temperature present optical nonlinearities are discussed. In particular, the Cr-ion induced charge transfer and corresponding vibronic excitons are discussed to be responsible for the fundamental absorption edge shift. The same clusters of charge transfer vibronic excitons induced by Cr3+-ions can be seen as an origin of drastical phase transition point shifts in SBN:Cr. This work is supported by DFG (SFB 225/C7), NATO Linkage Grant HTECH LG960540 and DFG 436RUS113/341/1(R).