U.S.-Hungary Materials Research on Point Defects in Optical Crystals

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The primary objective of this U.S.-Hungary research project between Dr. Lawrence A. Kappers of the University of Connecticut and Dr. I. Foldvari of the Research Laboratory for Crystal Physics, Budapest is to study the defect properties of nonlinear optical crystals. Specific materials to be investigated include doped and undoped single crystals of a new bismuth oxide, Bi2TeO5 as well as other materials that possess an intrinsic luminescence, (ZnWO4, Bi4Ge3O12, Bi12GeO20, Bi12SiO20 and Bi12TiO20). Single crystals will be grown at the Research Laboratory for Crystal Physics in Hungary using the Czochralski technique while crystal characterization will be performed at the University of Connecticut before and after electron irradiation using electron paramagnetic resonance, optical and spectroscopy. The experimental efforts will include studies of point defects and their involvement in scintillation, photorefractive, and photochromic processes in these materials. Comparisons of the results for the different crystals will contribute to our basic understanding of these phenomena. In addition, complementary theoretical studies will build upon results of the researchers' previous collaboration on cluster modeling of defects in paratellurite and will extend those methods to Bi2TeO5. Overall, combined results should improve our knowledge of those oxide crystals with properties that also have a potential for applications in optical devices. This project in condensed matter physics fulfills the program objectives of advancing science by enabling leading experts in the U.S. and Hungary to combine complementary talents and pool research resources in the areas of strong mutual interest and competence.