Regensburg 2007 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 9: Electric, Electromechanical and Optical Properties I

DF 9.4: Talk

Thursday, March 29, 2007, 11:20–11:40, H48

Extrinsic defects in high quality CaF₂ crystals for optical applications — •Stephan Hausfeld, Janis Sils, and Michael Reichling — Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany

Oxygen defects and other impurities were detected in CaF₂ single crystals by a highly sensitive method of photoluminescence under excitation by ultrashort UV laser pulses. To identify oxygen defects the luminescence was measured before and after annealing the crystal at 650^∘C and quenching it to room temperature. Only after this treatment luminescence of oxygen-vacancy dipoles in CaF₂ is visible. This observation can be explained by the dissociation of dipole dimers which do not contribute to the observed luminescence into simple oxygen-vacancy dipoles due to annealing and quenching. As major other impurities we identified Terbium, Cerium and Europium. Almost no luminescence of any impurity can be found in our crystals of highest quality. Only the oxygen defects remain as trace impurities in these samples.