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DF: Fachverband Dielektrische Festkörper

DF 14: Photonic Dielectrics III

DF 14.6: Vortrag

Donnerstag, 26. März 2009, 12:00–12:20, WIL A317

Optical cleaning of lithium niobate crystals for suppression of optical damage* — •Carsten Becher¹, Michael Kösters¹, Daniel Haertle¹, Boris Sturman², and Karsten Buse¹ — ¹Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn, Germany — ²Institute of Automation and Electrometry, Novosibirsk 630090, Russia

Lithium niobate (LiNbO₃) is a promising material for optical applications, e.g., electro-optic modulation, holography, and frequency conversion. However, the photorefractive effect in its unwanted form, the so-called “optical damage”, still inhibits the use of undoped LiNbO₃ at high light intensities: Light-induced refractive index changes cause deteriorations of the light beam and, e.g., disturb quasi-phase-matching, thus limiting the efficiency of non-linear optical processes. Optical cleaning as a method for suppression of optical damage in congruent, undoped LiNbO₃ crystals is presented: At sufficiently high temperatures, photo-excitable electrons are removed from an area illuminated by visible light due to the bulk-photovoltaic effect. While at room temperature, an arising electric field would quickly block the photovoltaic drift, at elevated temperatures, H⁺-ions are mobile and can compensate for this electric field. Optical cleaning is studied by two independent methods: Determination of the threshold-intensities for beam fanning, as well as measurements of birefringence changes.
*Financial support from the Deutsche Forschungsgemeinschaft (FOR 557) and from the Deutsche Telekom AG is gratefully acknowledged.